Device and methods for sealing and encapsulation for biocompatible energization elements

ABSTRACT

Device and methods for sealing and encapsulation for biocompatible energization elements are described. In some examples, the device and methods for sealing and encapsulation for biocompatible energization elements involve heat welding, laser welding, or both where a laminar structure is enclosed by a polymer film capable of sealing. In some examples, a field of use for the apparatus and methods may include any biocompatible device or product that requires energization elements.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation application of U.S. patentapplication Ser. No. 14/827,613 filed Aug. 17, 2015 which claims thebenefit of U.S. Provisional Application No. 62/040,178 filed Aug. 21,2014. The contents of each are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

A device and methods for sealing and encapsulation for biocompatibleenergization elements are described. In some examples, a field of usefor the device and methods for sealing and encapsulation forbiocompatible energization elements may include any biocompatible deviceor product that requires energy.

2. Description of the Related Art

Recently, the number of medical devices and their functionality hasbegun to rapidly develop. These medical devices may include, forexample, implantable pacemakers, electronic pills for monitoring and/ortesting a biological function, surgical devices with active components,contact lenses, infusion pumps, and neurostimulators. Addedfunctionality and an increase in performance to many of theaforementioned medical devices has been theorized and developed.However, to achieve the theorized added functionality, many of thesedevices now require self-contained energization means that arecompatible with the size and shape requirements of these devices, aswell as the energy requirements of the new energized components.

Some medical devices may include electrical components such assemiconductor devices that perform a variety of functions and may beincorporated into many biocompatible and/or implantable devices.However, such semiconductor components require energy and, thus,energization elements should preferably also be included in suchbiocompatible devices. The topology and relatively small size of thebiocompatible devices may create challenging environments for thedefinition of various functionalities. In many examples, it may beimportant to provide safe, reliable, compact and cost effective means toenergize the semiconductor components within the biocompatible devices.Therefore, a need exists for biocompatible energization elements formedfor implantation within or upon biocompatible devices where thestructure of the millimeter or smaller sized energization elementsprovides enhanced function for the energization element whilemaintaining biocompatibility.

Further, these energization elements may need to be protected from theirenvironment in order to maintain functionality and performance. This mayinclude fluid leaking into or out of the energization element. Forexample, a biocompatible battery placed in a contact lens may be exposedto tear fluid, which may potentially result in the fluid contacting bothcathode and anode, thus shorting the battery. Therefore, a need existsfor protecting energization elements from the outside environment.

SUMMARY OF THE INVENTION

Accordingly, devices and methods for sealing and encapsulation forbiocompatible energization elements are disclosed which affordelectrochemical and biocompatible advantages while maintaining thebiocompatibility, performance and function necessary for biocompatibleenergization elements.

One general aspect comprises a biocompatible energization elementencapsulated by a polymer film capable of sealing. The polymer filmcapable of sealing may be treated to form a seal with itself and withelements of the biocompatible energization element. Further, the polymerfilm capable of sealing may form an encapsulation around theenergization element while maintaining a cavity structure within thebiocompatible energization element. The biocompatible energizationelement may comprise: a first and second current collector, a cathode,an anode, an electrolyte, and a laminar structure including a cavity.

Implementations of the biocompatible energization element may compriseone or more of the following features. The polymer film capable ofsealing may comprise polypropylene. The polymer film capable of sealingmay be treated by a means of welding. The polymer film capable ofsealing may be further adhered to the biocompatible energization elementwith adhesive. The polymer film capable of sealing may be welded to aseparator contained within the biocompatible energization element. Thepolymer film capable of sealing may be welded to a separator shelfcontained within the biocompatible energization element. The polymerfilm capable of sealing may be welded to a current collector of thebiocompatible energization element. The biocompatible energizationelement may be used in a biomedical device. The biomedical device may bean ophthalmic device. The ophthalmic device may be a contact lens.

Another general aspect comprises a method for encapsulating abiocompatible energization element, wherein the method comprises:obtaining a first polymer film capable of sealing; placing a firstcurrent collector upon the first polymer capable of sealing; placing afirst electrode upon the first current collector; placing a separatorshelf upon the first current collector where the separator shelfsurrounds the first electrode and where the separator shelf creates adefined cavity within the laminar structure; placing a separator uponthe separator shelf where the separator will enclose the first electrodeinside the cavity; placing a second electrode upon the separator;placing a second polymer capable of sealing upon the second currentcollector; and sealing together the first and second polymer capable ofsealing to form a sealed and encapsulated energization element. Thebiocompatible energization element may comprise: a first and secondcurrent collector, a cathode, an anode, an electrolyte, and a laminarstructure comprising a cavity.

Implementations of the method for encapsulating a biocompatibleenergization element may comprise one or more of the following features.The first and second polymer layers may comprise polypropylene. Thesealing together of the first and second polymer capable of sealing maycomprise welding. The sealing together of the first and second polymercapable of sealing may comprise adhering the first and second polymercapable of sealing with adhesive. The first and second polymer capableof sealing may comprise a combination of adhesives and welding of thefirst and second polymer capable of sealing. The method may furthercomprise adhering the first and second current collectors to theseparator shelf with adhesive. The method may further comprise adheringthe polymer film capable of sealing to the biocompatible energizationelement with adhesive. The method may further comprise metalizing apolymer film capable of sealing to form a metalized polymer film. Themethod may further comprise sealing the metalized polymer film with theenergization element by welding. The method may further comprise sealingthe metalized polymer film to a current collector by welding. The methodmay further comprise placing the biocompatible energization element intoan insert. The method may also comprise placing the insert into abiomedical device. The biomedical device may be an ophthalmic device.The ophthalmic device may be a contact lens.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the invention will beapparent from the following, more particular description of preferredembodiments of the invention, as illustrated in the accompanyingdrawings.

FIGS. 1A-1D illustrate exemplary aspects of biocompatible energizationelements in concert with the exemplary application of contact lenses.

FIG. 2 illustrates the exemplary size and shape of individual cells ofan exemplary battery design.

FIG. 3A illustrates a first stand-alone, packaged biocompatibleenergization element with exemplary anode and cathode connections.

FIG. 3B illustrates a second stand-alone, packaged biocompatibleenergization element with exemplary anode and cathode connections.

FIGS. 4A-4N illustrate exemplary method steps for the formation ofbiocompatible energization elements for biomedical devices.

FIG. 5 illustrates an exemplary fully formed biocompatible energizationelement.

FIGS. 6A-6F illustrate exemplary method steps for structural formationof biocompatible energization elements.

FIGS. 7A-7F illustrate exemplary method steps for structural formationof biocompatible energization elements utilizing an alternateelectroplating method.

FIGS. 8A-8H illustrate exemplary method steps for the formation ofbiocompatible energization elements with hydrogel separator forbiomedical devices.

FIGS. 9A-9C illustrate exemplary methods steps for the structuralformation of biocompatible energization elements utilizing alternativehydrogel processing examples.

FIGS. 10A-10F illustrate optimized and non-optimized depositing of acathode mixture into a cavity.

FIG. 11 illustrates agglomeration of a cathode mixture inside of acavity.

FIGS. 12A-12F illustrate exemplary use of a gelled electrolyte in abiocompatible energization element.

FIGS. 13A-13C illustrate exemplary designs for sealing and encapsulatinga biocompatible energization element.

FIGS. 14A-14I illustrate exemplary method steps for sealing andencapsulating a biocompatible energization element.

FIGS. 15A-15D illustrate exemplary cross-sectional views of an exemplaryenergization element.

FIGS. 16A-16G illustrate alternate exemplary method steps for sealingand encapsulating a biocompatible energization element.

DETAILED DESCRIPTION OF THE INVENTION

Biofuel cells for use in a biocompatible battery are disclosed in thisapplication. In the following sections, detailed descriptions of variousexamples are described. The descriptions of examples are exemplaryembodiments only, and various modifications and alterations may beapparent to those skilled in the art. Therefore, the examples do notlimit the scope of this application. The biofuel cells, and thestructures that contain them, may be designed for use in biocompatiblebatteries. In some examples, these biocompatible batteries may bedesigned for use in, or proximate to, the body of a living organism.

Glossary

In the description and claims below, various terms may be used for whichthe following definitions will apply:

“Anode” as used herein refers to an electrode through which electriccurrent flows into a polarized electrical device. The direction ofelectric current is typically opposite to the direction of electronflow. In other words, the electrons flow from the anode into, forexample, an electrical circuit.

“Binder” as used herein refers to a polymer that is capable ofexhibiting elastic responses to mechanical deformations and that ischemically compatible with other energization element components. Forexample, binders may include electroactive materials, electrolytes,polymers, and the like.

“Biocompatible” as used herein refers to a material or device thatperforms with an appropriate host response in a specific application.For example, a biocompatible device does not have toxic or injuriouseffects on biological systems.

“Cathode” as used herein refers to an electrode through which electriccurrent flows out of a polarized electrical device. The direction ofelectric current is typically opposite to the direction of electronflow. Therefore, the electrons flow into the cathode of the polarizedelectrical device, and out of, for example, the connected electricalcircuit.

“Coating” as used herein refers to a deposit of material in thin forms.In some uses, the term will refer to a thin deposit that substantiallycovers the surface of a substrate it is formed upon. In other morespecialized uses, the term may be used to describe small thin depositsin smaller regions of the surface.

“Electrode” as used herein may refer to an active mass in the energysource. For example, it may include one or both of the anode andcathode.

“Energized” as used herein refers to the state of being able to supplyelectrical current or to have electrical energy stored within.

“Energy” as used herein refers to the capacity of a physical system todo work. Many uses of the energization elements may relate to thecapacity of being able to perform electrical actions.

“Energy Source” or “Energization Element” or “Energization Device” asused herein refers to any device or layer which is capable of supplyingenergy or placing a logical or electrical device in an energized state.The energization elements may include batteries. The batteries may beformed from alkaline type cell chemistry and may be solid-statebatteries or wet cell batteries.

“Fillers” as used herein refer to one or more energization elementseparators that do not react with either acid or alkaline electrolytes.Generally, fillers may include substantially water insoluble materialssuch as carbon black; coal dust; graphite; metal oxides and hydroxidessuch as those of silicon, aluminum, calcium, magnesium, barium,titanium, iron, zinc, and tin; metal carbonates such as those of calciumand magnesium; minerals such as mica, montmorillonite, kaolinite,attapulgite, and talc; synthetic and natural zeolites such as Portlandcement; precipitated metal silicates such as calcium silicate; hollow orsolid polymer or glass microspheres, flakes and fibers; and the like.

“Functionalized” as used herein refers to making a layer or device ableto perform a function including, for example, energization, activation,and/or control.

“Ionizing Salt” as used herein refers to an ionic solid that willdissolve in a solvent to produce dissolved ions in solution. In numerousexamples, the solvent may comprise water.

“Mold” as used herein refers to a rigid or semi-rigid object that may beused to form three-dimensional objects from uncured formulations. Someexemplary molds include two mold parts that, when opposed to oneanother, define the structure of a three-dimensional object.

“Power” as used herein refers to work done or energy transferred perunit of time.

“Rechargeable” or “Re-energizable” as used herein refer to a capabilityof being restored to a state with higher capacity to do work. Many usesmay relate to the capability of being restored with the ability to flowelectrical current at a certain rate for certain, reestablished timeperiods.

“Reenergize” or “Recharge” as used herein refer to restoring to a statewith higher capacity to do work. Many uses may relate to restoring adevice to the capability to flow electrical current at a certain ratefor a certain reestablished time period.

“Released” as used herein and sometimes referred to as “released from amold” means that a three-dimensional object is either completelyseparated from the mold, or is only loosely attached to the mold, sothat it may be removed with mild agitation.

“Separator shelf” as used herein means an element of a biocompatibleenergization element used to avoid edge shorting around the separator byimplementing A cut separator, liquid separator or combination of thetwo. A separator shelf may be a polymer such as polypropylene, machined(e.g. laser) and placed within the cell construct. It needs to be amaterial that can seal to the top and bottom package films. It may beanother material such as glass or ceramic as long as it can be cut andsealed. Adhesive, lacquer, epoxy, asphalt, etc. may be used incombination with a rigid separator shelf.

“Stacked” as used herein means to place at least two component layers inproximity to each other such that at least a portion of one surface ofone of the layers contacts a first surface of a second layer. In someexamples, a coating, whether for adhesion or other functions, may residebetween the two layers that are in contact with each other through saidcoating.

“Traces” as used herein refer to energization element components capableof connecting together the circuit components. For example, circuittraces may include copper or gold when the substrate is a printedcircuit board and may typically be copper, gold or printed film in aflexible circuit. A special type of “Trace” is the current collector.Current collectors are traces with electrochemical compatibility thatmake the current collectors suitable for use in conducting electrons toand from an anode or cathode in the presence of electrolyte.

The methods and apparatus presented herein relate to formingbiocompatible energization elements for inclusion within or on flat orthree-dimensional biocompatible devices. A particular class ofenergization elements may be batteries that are fabricated in layers.The layers may also be classified as laminate layers. A battery formedin this manner may be classified as a laminar battery.

There may be other examples of how to assemble and configure batteriesaccording to the present invention, and some may be described infollowing sections. However, for many of these examples, there areselected parameters and characteristics of the batteries that may bedescribed in their own right. In the following sections, somecharacteristics and parameters will be focused upon.

Exemplary Biomedical Device Construction with Biocompatible EnergizationElements

An example of a biomedical device that may incorporate the EnergizationElements, batteries, of the present invention may be an electroactivefocal-adjusting contact lens. Referring to FIG. 1A, an example of such acontact lens insert may be depicted as contact lens insert 100. In thecontact lens insert 100, there may be an electroactive element 120 thatmay accommodate focal characteristic changes in response to controllingvoltages. A circuit 105, to provide those controlling voltage signals aswell as to provide other functions such as controlling sensing of theenvironment for external control signals, may be powered by abiocompatible battery element 110. As depicted in FIG. 1A, the batteryelement 110 may be found as multiple major pieces, in this case threepieces, and may include the various configurations of battery chemistryelements as discussed herein. The battery elements 110 may have variousinterconnect features to join together pieces as may be depictedunderlying the region of interconnect 114. The battery elements 110 maybe connected to a circuit element that may have its own substrate 111upon which interconnect features 125 may be located. The circuit 105,which may be in the form of an integrated circuit, may be electricallyand physically connected to the substrate 111 and its interconnectfeatures 125.

Referring to FIG. 1B, a cross sectional relief of a contact lens 150 maycomprise contact lens insert 100 and its discussed constituents. Thecontact lens insert 100 may be encapsulated into a skirt of contact lenshydrogel 155 which may encapsulate the contact lens insert 100 andprovide a comfortable interface of the contact lens 150 to a user's eye.

In reference to concepts of the present invention, the battery elementsmay be formed in a two-dimensional form as depicted in FIG. 1C. In thisdepiction there may be two main regions of battery cells in the regionsof battery component 165 and the second battery component in the regionof battery chemistry element 160. The battery elements, which aredepicted in flat form in FIG. 1C, may connect to a circuit element 163,which in the example of FIG. 1C may comprise two major circuit areas167. The circuit element 163 may connect to the battery element at anelectrical contact 161 and a physical contact 162. The flat structuremay be folded into a three-dimensional conical structure as has beendescribed with respect to the present invention. In that process asecond electrical contact 166 and a second physical contact 164 may beused to connect and physically stabilize the three-dimensionalstructure. Referring to FIG. 1D, a representation of thisthree-dimensional conical structure 180 may be found. The physical andelectrical contact points 181 may also be found and the illustration maybe viewed as a three-dimensional view of the resulting structure. Thisstructure may include the modular electrical and battery component thatwill be incorporated with a lens insert into a biocompatible device.

Segmented Battery Schemes

Referring to FIG. 2, an example of different types of segmented batteryschemes is depicted for an exemplary battery element for a contact lenstype example. The segmented components may be relatively circular-shaped271, square-shaped 272 or rectangular-shaped. In rectangular-shapedexamples, the rectangles may be small rectangular shapes 273, largerrectangular shapes 274, or even larger rectangular shapes 275.

Custom Shapes of Flat Battery Elements

In some examples of biocompatible batteries, the batteries may be formedas flat elements. Referring to FIG. 3A, an example of a rectangularoutline 310 of the battery element may be depicted with an anodeconnection 311 and a cathode connection 312. Referring to FIG. 3B, anexample of a circular outline 330 of a battery element may be depictedwith an anode connection 331 and a cathode connection 332.

In some examples of flat-formed batteries, the outlines of the batteryform may be dimensionally and geometrically configured to fit in customproducts. In addition to examples with rectangular or circular outlines,custom “free-form” or “free shape” outlines may be formed which mayallow the battery configuration to be optimized to fit within a givenproduct.

In the exemplary biomedical device case of a variable optic, a“free-form” example of a flat outline may be arcuate in form. The freeform may be of such geometry that when formed to a three-dimensionalshape, it may take the form of a conical, annular skirt that fits withinthe constraining confines of a contact lens. It may be clear thatsimilar beneficial geometries may be formed where medical devices haverestrictive 2D or 3D shape requirements.

Biocompatibility Aspects of Batteries

As an example, the batteries according to the present invention may haveimportant aspects relating to safety and biocompatibility. In someexamples, batteries for biomedical devices may need to meet requirementsabove and beyond those for typical usage scenarios. In some examples,design aspects may be considered related to stressing events. Forexample, the safety of an electronic contact lens may need to beconsidered in the event a user breaks the lens during insertion orremoval. In another example, design aspects may consider the potentialfor a user to be struck in the eye by a foreign object. Still furtherexamples of stressful conditions that may be considered in developingdesign parameters and constraints may relate to the potential for a userto wear the lens in challenging environments like the environment underwater or the environment at high altitude in non-limiting examples.

The safety of such a device may be influenced by the materials that thedevice is formed with or from, by the quantities of those materialsemployed in manufacturing the device, and also by the packaging appliedto separate the devices from the surrounding on- or in-body environment.In an example, pacemakers may be a typical type of biomedical devicewhich may include a battery and which may be implanted in a user for anextended period of time. Accordingly, in some examples, such pacemakersmay typically be packaged with welded, hermetic titanium enclosures, orin other examples, multiple layers of encapsulation. Emerging poweredbiomedical devices may present new challenges for packaging, especiallybattery packaging. These new devices may be much smaller than existingbiomedical devices, for example, an electronic contact lens or pillcamera may be significantly smaller than a pacemaker. In such examples,the volume and area available for packaging may be greatly reduced.

Electrical Requirements of Microbatteries

Another area for design considerations may relate to electricalrequirements of the device, which may be provided by the battery. Inorder to function as a power source for a medical device, an appropriatebattery may need to meet the full electrical requirements of the systemwhen operating in a non-connected or non-externally powered mode. Anemerging field of non-connected or non-externally powered biomedicaldevices may include, for example, vision-correcting contact lenses,health monitoring devices, pill cameras, and novelty devices. Recentdevelopments in integrated circuit (IC) technology may permit meaningfulelectrical operation at very low current levels, for example, picoampsof standby current and microamps of operating current. IC's may alsopermit very small devices.

Microbatteries for biomedical applications may be required to meet manysimultaneous, challenging requirements. For example, the microbatterymay be required to have the capability to deliver a suitable operatingvoltage to an incorporated electrical circuit. This operating voltagemay be influenced by several factors including the IC process “node,”the output voltage from the circuit to another device, and a particularcurrent consumption target which may also relate to a desired devicelifetime.

With respect to the IC process, nodes may typically be differentiated bythe minimum feature size of a transistor, such as its “so-called”transistor channel. This physical feature, along with other parametersof the IC fabrication, such as gate oxide thickness, may be associatedwith a resulting rating standard for “turn-on” or “threshold” voltagesof field-effect transistors (FET's) fabricated in the given processnode. For example, in a node with a minimum feature size of 0.5 microns,it may be common to find FET's with turn-on voltages of 5.0V. However,at a minimum feature size of 90 nm, the FET's may turn-on at 1.2, 1.8,and 2.5V. The IC foundry may supply standard cells of digital blocks,for example, inverters and flip-flops that have been characterized andare rated for use over certain voltage ranges. Designers chose an ICprocess node based on several factors including density of digitaldevices, analog/digital mixed signal devices, leakage current, wiringlayers, and availability of specialty devices such as high-voltageFET's. Given these parametric aspects of the electrical components,which may draw power from a microbattery, it may be important for themicrobattery power source to be matched to the requirements of thechosen process node and IC design, especially in terms of availablevoltage and current.

In some examples, an electrical circuit powered by a microbattery, mayconnect to another device. In non-limiting examples, themicrobattery-powered electrical circuit may connect to an actuator or atransducer. Depending on the application, these may include alight-emitting diode (LED), a sensor, a microelectromechanical system(MEMS) pump, or numerous other such devices. In some examples, suchconnected devices may require higher operating voltage conditions thancommon IC process nodes. For example, a variable-focus lens may require35V to activate. The operating voltage provided by the battery maytherefore be a critical consideration when designing such a system. Insome examples of this type of consideration, the efficiency of a lensdriver to produce 35V from a 1V battery may be significantly less thanit might be when operating from a 2V battery. Further requirements, suchas die size, may be dramatically different considering the operatingparameters of the microbattery as well.

Individual battery cells may typically be rated with open-circuit,loaded, and cutoff voltages. The open-circuit voltage is the potentialproduced by the battery cell with infinite load resistance. The loadedvoltage is the potential produced by the cell with an appropriate, andtypically also specified, load impedance placed across the cellterminals. The cutoff voltage is typically a voltage at which most ofthe battery has been discharged. The cutoff voltage may represent avoltage, or degree of discharge, below which the battery should not bedischarged to avoid deleterious effects such as excessive gassing. Thecutoff voltage may typically be influenced by the circuit to which thebattery is connected, not just the battery itself, for example, theminimum operating voltage of the electronic circuit. In one example, analkaline cell may have an open-circuit voltage of 1.6V, a loaded voltagein the range 1.0 to 1.5V, and a cutoff voltage of 1.0V. The voltage of agiven microbattery cell design may depend upon other factors of the cellchemistry employed. And, different cell chemistry may therefore havedifferent cell voltages.

Cells may be connected in series to increase voltage; however, thiscombination may come with tradeoffs to size, internal resistance, andbattery complexity. Cells may also be combined in parallelconfigurations to decrease resistance and increase capacity; however,such a combination may tradeoff size and shelf life.

Battery capacity may be the ability of a battery to deliver current, ordo work, for a period of time. Battery capacity may typically bespecified in units such as microamp-hours. A battery that may deliver 1microamp of current for 1 hour has 1 microamp-hour of capacity. Capacitymay typically be increased by increasing the mass (and hence volume) ofreactants within a battery device; however, it may be appreciated thatbiomedical devices may be significantly constrained on available volume.Battery capacity may also be influenced by electrode and electrolytematerial.

Depending on the requirements of the circuitry to which the battery isconnected, a battery may be required to source current over a range ofvalues. During storage prior to active use, a leakage current on theorder of picoamps to nanoamps may flow through circuits, interconnects,and insulators. During active operation, circuitry may consume quiescentcurrent to sample sensors, run timers, and perform such low powerconsumption functions. Quiescent current consumption may be on the orderof nanoamps to milliamps. Circuitry may also have even higher peakcurrent demands, for example, when writing flash memory or communicatingover radio frequency (RF). This peak current may extend to tens ofmilliamps or more. The resistance and impedance of a microbattery devicemay also be important to design considerations.

Shelf life typically refers to the period of time which a battery maysurvive in storage and still maintain useful operating parameters. Shelflife may be particularly important for biomedical devices for severalreasons. Electronic devices may displace non-powered devices, as forexample may be the case for the introduction of an electronic contactlens. Products in these existing market spaces may have establishedshelf life requirements, for example, three years, due to customer,supply chain, and other requirements. It may typically be desired thatsuch specifications not be altered for new products. Shelf liferequirements may also be set by the distribution, inventory, and usemethods of a device including a microbattery. Accordingly,microbatteries for biomedical devices may have specific shelf liferequirements, which may be, for example, measured in the number ofyears.

In some examples, three-dimensional biocompatible energization elementsmay be rechargeable. For example, an inductive coil may also befabricated on the three-dimensional surface. The inductive coil couldthen be energized with a radio-frequency (“RF”) fob. The inductive coilmay be connected to the three-dimensional biocompatible energizationelement to recharge the energization element when RF is applied to theinductive coil. In another example, photovoltaics may also be fabricatedon the three-dimensional surface and connected to the three-dimensionalbiocompatible energization element. When exposed to light or photons,the photovoltaics will produce electrons to recharge the energizationelement.

In some examples, a battery may function to provide the electricalenergy for an electrical system. In these examples, the battery may beelectrically connected to the circuit of the electrical system. Theconnections between a circuit and a battery may be classified asinterconnects. These interconnects may become increasingly challengingfor biomedical microbatteries due to several factors. In some examples,powered biomedical devices may be very small thus allowing little areaand volume for the interconnects. The restrictions of size and area mayimpact the electrical resistance and reliability of theinterconnections.

In other respects, a battery may contain a liquid electrolyte whichcould boil at high temperature. This restriction may directly competewith the desire to use a solder interconnect which may, for example,require relatively high temperatures such as 250 degrees Celsius tomelt. Although in some examples, the battery chemistry, including theelectrolyte, and the heat source used to form solder basedinterconnects, may be isolated spatially from each other. In the casesof emerging biomedical devices, the small size may preclude theseparation of electrolyte and solder joints by sufficient distance toreduce heat conduction.

Interconnects

Interconnects may allow current to flow to and from the battery inconnection with an external circuit. Such interconnects may interfacewith the environments inside and outside the battery, and may cross theboundary or seal between those environments. These interconnects may beconsidered as traces, making connections to an external circuit, passingthrough the battery seal, and then connecting to the current collectorsinside the battery. As such, these interconnects may have severalrequirements. Outside the battery, the interconnects may resembletypical printed circuit traces. They may be soldered to, or otherwiseconnect to, other traces. In an example where the battery is a separatephysical element from a circuit board comprising an integrated circuit,the battery interconnect may allow for connection to the externalcircuit. This connection may be formed with solder, conductive tape,conductive ink or epoxy, or other means. The interconnect traces mayneed to survive in the environment outside the battery, for example, notcorroding in the presence of oxygen.

As the interconnect passes through the battery seal, it may be ofcritical importance that the interconnect coexist with the seal andpermit sealing. Adhesion may be required between the seal andinterconnect in addition to the adhesion which may be required betweenthe seal and battery package. Seal integrity may need to be maintainedin the presence of electrolyte and other materials inside the battery.Interconnects, which may typically be metallic, may be known as pointsof failure in battery packaging. The electrical potential and/or flow ofcurrent may increase the tendency for electrolyte to “creep” along theinterconnect. Accordingly, an interconnect may need to be engineered tomaintain seal integrity.

Inside the battery, the interconnects may interface with the currentcollectors or may actually form the current collectors. In this regard,the interconnect may need to meet the requirements of the currentcollectors as described herein, or may need to form an electricalconnection to such current collectors.

One class of candidate interconnects and current collectors is metalfoils. Such foils are available in thickness of 25 microns or less,which make them suitable for very thin batteries. Such foil may also besourced with low surface roughness and contamination, two factors whichmay be critical for battery performance. The foils may include zinc,nickel, brass, copper, titanium, other metals, and various alloys.

Modular Battery Components

In some examples, a modular battery component may be formed according tosome aspects and examples of the present invention. In these examples,the modular battery assembly may be a separate component from otherparts of the biomedical device. In the example of an ophthalmic contactlens device, such a design may include a modular battery that isseparate from the rest of a media insert. There may be numerousadvantages of forming a modular battery component. For example, in theexample of the contact lens, a modular battery component may be formedin a separate, non-integrated process which may alleviate the need tohandle rigid, three-dimensionally formed optical plastic components. Inaddition, the sources of manufacturing may be more flexible and mayoperate in a more parallel mode to the manufacturing of the othercomponents in the biomedical device. Furthermore, the fabrication of themodular battery components may be decoupled from the characteristics ofthree-dimensional (3D) shaped devices. For example, in applicationsrequiring three-dimensional final forms, a modular battery system may befabricated in a flat or roughly two-dimensional (2D) perspective andthen shaped to the appropriate three-dimensional shape. A modularbattery component may be tested independently of the rest of thebiomedical device and yield loss due to battery components may be sortedbefore assembly. The resulting modular battery component may be utilizedin various media insert constructs that do not have an appropriate rigidregion upon which the battery components may be formed; and, in a stillfurther example, the use of modular battery components may facilitatethe use of different options for fabrication technologies than mightotherwise be utilized, such as, web-based technology (roll to roll),sheet-based technology (sheet-to-sheet), printing, lithography, and“squeegee” processing. In some examples of a modular battery, thediscrete containment aspect of such a device may result in additionalmaterial being added to the overall biomedical device construct. Sucheffects may set a constraint for the use of modular battery solutionswhen the available space parameters require minimized thickness orvolume of solutions.

Battery shape requirements may be driven at least in part by theapplication for which the battery is to be used. Traditional batteryform factors may be cylindrical forms or rectangular prisms, made ofmetal, and may be geared toward products which require large amounts ofpower for long durations. These applications may be large enough thatthey may comprise large form factor batteries. In another example,planar (2D) solid-state batteries are thin rectangular prisms, typicallyformed upon inflexible silicon or glass. These planar solid-statebatteries may be formed in some examples using silicon wafer-processingtechnologies. In another type of battery form factor, low power,flexible batteries may be formed in a pouch construct, using thin foilsor plastic to contain the battery chemistry. These batteries may be madeflat (2D), and may be designed to function when bowed to a modestout-of-plane (3D) curvature.

In some of the examples of the battery applications in the presentinvention where the battery may be employed in a variable optic lens,the form factor may require a three-dimensional curvature of the batterycomponent where a radius of that curvature may be on the order ofapproximately 8.4 mm. The nature of such a curvature may be consideredto be relatively steep and for reference may approximate the type ofcurvature found on a human fingertip. The nature of a relative steepcurvature creates challenging aspects for manufacture. In some examplesof the present invention, a modular battery component may be designedsuch that it may be fabricated in a flat, two-dimensional manner andthen formed into a three-dimensional form of relative high curvature.

Battery Module Thickness

In designing battery components for biomedical applications, tradeoffsamongst the various parameters may be made balancing technical, safetyand functional requirements. The thickness of the battery component maybe an important and limiting parameter. For example, in an optical lensapplication the ability of a device to be comfortably worn by a user mayhave a critical dependence on the thickness across the biomedicaldevice. Therefore, there may be critical enabling aspects in designingthe battery for thinner results. In some examples, battery thickness maybe determined by the combined thicknesses of top and bottom sheets,spacer sheets, and adhesive layer thicknesses. Practical manufacturingaspects may drive certain parameters of film thickness to standardvalues in available sheet stock. In addition, the films may have minimumthickness values to which they may be specified base upon technicalconsiderations relating to chemical compatibility, moisture/gasimpermeability, surface finish, and compatibility with coatings that maybe deposited upon the film layers.

In some examples, a desired or goal thickness of a finished batterycomponent may be a component thickness that is less than 220 μm. Inthese examples, this desired thickness may be driven by thethree-dimensional geometry of an exemplary ophthalmic lens device wherethe battery component may need to be fit inside the available volumedefined by a hydrogel lens shape given end user comfort,biocompatibility, and acceptance constraints. This volume and its effecton the needs of battery component thickness may be a function of totaldevice thickness specification as well as device specification relatingto its width, cone angle, and inner diameter. Another important designconsideration for the resulting battery component design may relate tothe volume available for active battery chemicals and materials in agiven battery component design with respect to the resulting chemicalenergy that may result from that design. This resulting chemical energymay then be balanced for the electrical requirements of a functionalbiomedical device for its targeted life and operating conditions

Battery Module Flexibility

Another dimension of relevance to battery design and to the design ofrelated devices that utilize battery based energy sources is theflexibility of the battery component. There may be numerous advantagesconferred by flexible battery forms. For example, a flexible batterymodule may facilitate the previously mentioned ability to fabricate thebattery form in a two-dimensional (2D) flat form. The flexibility of theform may allow the two-dimensional battery to then be formed into anappropriate 3D shape to fit into a biomedical device such as a contactlens.

In another example of the benefits that may be conferred by flexibilityin the battery module, if the battery and the subsequent device isflexible then there may be advantages relating to the use of the device.In an example, a contact lens form of a biomedical device may haveadvantages for insertion/removal of the media insert based contact lensthat may be closer to the insertion/removal of a standard, non-filledhydrogel contact lens.

The number of flexures may be important to the engineering of thebattery. For example, a battery which may only flex one time from aplanar form into a shape suitable for a contact lens may havesignificantly different design from a battery capable of multipleflexures. The flexure of the battery may also extend beyond the abilityto mechanically survive the flexure event. For example, an electrode maybe physically capable of flexing without breaking, but the mechanicaland electrochemical properties of the electrode may be altered byflexure. Flex-induced changes may appear instantly, for example, aschanges to impedance, or flexure may introduce changes which are onlyapparent in long-term shelf life testing.

Battery Module Width

There may be numerous applications into which the biocompatibleenergization elements or batteries of the present invention may beutilized. In general, the battery width requirement may be largely afunction of the application in which it is applied. In an exemplarycase, a contact lens battery system may have constrained needs for thespecification on the width of a modular battery component. In someexamples of an ophthalmic device where the device has a variable opticfunction powered by a battery component, the variable optic portion ofthe device may occupy a central spherical region of about 7.0 mm indiameter. The exemplary battery elements may be considered as athree-dimensional object, which fits as an annular, conical skirt aroundthe central optic and formed into a truncated conical ring. If therequired maximum diameter of the rigid insert is a diameter of 8.50 mm,and tangency to a certain diameter sphere may be targeted (as forexample in a roughly 8.40 mm diameter), then geometry may dictate whatthe allowable battery width may be. There may be geometric models thatmay be useful for calculating desirable specifications for the resultinggeometry which in some examples may be termed a conical frustumflattened into a sector of an annulus.

Flattened battery width may be driven by two features of the batteryelement, the active battery components and seal width. In some examplesrelating to ophthalmic devices a target thickness may be between 0.100mm and 0.500 mm per side, and the active battery components may betargeted at approximately 0.800 mm wide. Other biomedical devices mayhave differing design constraints but the principles for flexible flatbattery elements may apply in similar fashion.

Cavities as Design Elements in Battery Component Design

In some examples, battery elements may be designed in manners thatsegment the regions of active battery chemistry. There may be numerousadvantages from the division of the active battery components intodiscrete segments. In a non-limiting example, the fabrication ofdiscrete and smaller elements may facilitate production of the elements.The function of battery elements including numerous smaller elements maybe improved. Defects of various kinds may be segmented andnon-functional elements may be isolated in some cases to result indecreased loss of function. This may be relevant in examples where theloss of battery electrolyte may occur. The isolation of individualizedcomponents may allow for a defect that results in leakage of electrolyteout of the critical regions of the battery to limit the loss of functionto that small segment of the total battery element whereas theelectrolyte loss through the defect could empty a significantly largerregion for batteries configured as a single cell. Smaller cells mayresult in lowered volume of active battery chemicals on an overallperspective, but the mesh of material surrounding each of the smallercells may result in a strengthening of the overall structure.

Battery Element Separators

Batteries of the type described in the present invention may utilize aseparator material that physically and electrically separates the anodeand anode current collector portions from the cathode and cathodecurrent collector portions. The separator may be a membrane that ispermeable to water and dissolved electrolyte components; however, it maytypically be electrically non-conductive. While a myriad ofcommercially-available separator materials may be known to those ofskill in the art, the novel form factor of the present invention maypresent unique constraints on the task of separator selection,processing, and handling.

Since the designs of the present invention may have ultra-thin profiles,the choice may be limited to the thinnest separator materials typicallyavailable. For example, separators of approximately 25 microns inthickness may be desirable. Some examples which may be advantageous maybe about 12 microns in thickness. There may be numerous acceptablecommercial separators include microfibrillated, microporous polyethylenemonolayer and/or polypropylene-polyethylene-polypropylene (PP/PE/PP)trilayer separator membranes such as those produced by Celgard(Charlotte, N.C.). A desirable example of separator material may beCelgard M824 PP/PE/PP trilayer membrane having a thickness of 12microns. Alternative examples of separator materials useful for examplesof the present invention may include separator membranes includingregenerated cellulose (e.g. cellophane).

While PP/PE/PP trilayer separator membranes may have advantageousthickness and mechanical properties, owing to their polyolefiniccharacter, they may also suffer from a number of disadvantages that mayneed to be overcome in order to make them useful in examples of thepresent invention. Roll or sheet stock of PP/PE/PP trilayer separatormaterials may have numerous wrinkles or other form errors that may bedeleterious to the micron-level tolerances applicable to the batteriesdescribed herein. Furthermore, polyolefin separators may need to be cutto ultra-precise tolerances for inclusion in the present designs, whichmay therefore implicate laser cutting as an exemplary method of formingdiscrete current collectors in desirable shapes with tight tolerances.Owing to the polyolefinic character of these separators, certain cuttinglasers useful for micro fabrication may employ laser wavelengths, e.g.355 nm, that will not cut polyolefins. The polyolefins do notappreciably absorb the laser energy and are thereby non-ablatable.Finally, polyolefin separators may not be inherently wettable to aqueouselectrolytes used in the batteries described herein.

Nevertheless, there may be methods for overcoming these inherentlimitations for polyolefinic type membranes. In order to present amicroporous separator membrane to a high-precision cutting laser forcutting pieces into arc segments or other advantageous separatordesigns, the membrane may need to be flat and wrinkle-free. If these twoconditions are not met, the separator membrane may not be fully cutbecause the cutting beam may be inhibited as a result of defocusing ofor otherwise scattering the incident laser energy. Additionally, if theseparator membrane is not flat and wrinkle-free, the form accuracy andgeometric tolerances of the separator membrane may not be sufficientlyachieved. Allowable tolerances for separators of current examples maybe, for example, +0 microns and −20 microns with respect tocharacteristic lengths and/or radii. There may be advantages for tightertolerances of +0 microns and −10 micron and further for tolerances of +0microns and −5 microns. Separator stock material may be made flat andwrinkle-free by temporarily laminating the material to a float glasscarrier with an appropriate low-volatility liquid. Low-volatilityliquids may have advantages over temporary adhesives due to thefragility of the separator membrane and due to the amount of processingtime that may be required to release separator membrane from an adhesivelayer. Furthermore, in some examples achieving a flat and wrinkle-freeseparator membrane on float glass using a liquid has been observed to bemuch more facile than using an adhesive. Prior to lamination, theseparator membrane may be made free of particulates. This may beachieved by ultrasonic cleaning of separator membrane to dislodge anysurface-adherent particulates. In some examples, handling of a separatormembrane may be done in a suitable, low-particle environment such as alaminar flow hood or a cleanroom of at least class 10,000. Furthermore,the float glass substrate may be made to be particulate free by rinsingwith an appropriate solvent, ultrasonic cleaning, and/or wiping withclean room wipes.

While a wide variety of low-volatility liquids may be used for themechanical purpose of laminating microporous polyolefin separatormembranes to a float glass carrier, specific requirements may be imposedon the liquid to facilitate subsequent laser cutting of discreteseparator shapes. One requirement may be that the liquid has a surfacetension low enough to soak into the pores of the separator materialwhich may easily be verified by visual inspection. In some examples, theseparator material turns from a white color to a translucent appearancewhen liquid fills the micropores of the material. It may be desirable tochoose a liquid that may be benign and “safe” for workers that will beexposed to the preparation and cutting operations of the separator. Itmay be desirable to choose a liquid whose vapor pressure may be lowenough so that appreciable evaporation does not occur during the timescale of processing (on the order of 1 day). Finally, in some examplesthe liquid may have sufficient solvating power to dissolve advantageousUV absorbers that may facilitate the laser cutting operation. In anexample, it has been observed that a 12 percent (w/w) solution ofavobenzone UV absorber in benzyl benzoate solvent may meet theaforementioned requirements and may lend itself to facilitating thelaser cutting of polyolefin separators with high precision and tolerancein short order without an excessive number of passes of the cuttinglaser beam. In some examples, separators may be cut with an 8 W 355 nmnanosecond diode-pumped solid state laser using this approach where thelaser may have settings for low power attenuation (e.g. 3 percentpower), a moderate speed of 1 to 10 mm/s, and only 1 to 3 passes of thelaser beam. While this UV-absorbing oily composition has been proven tobe an effective laminating and cutting process aid, other oilyformulations may be envisaged by those of skill in the art and usedwithout limitation.

In some examples, a separator may be cut while fixed to a float glass.One advantage of laser cutting separators while fixed to a float glasscarrier may be that a very high number density of separators may be cutfrom one separator stock sheet much like semiconductor die may bedensely arrayed on a silicon wafer. Such an approach may provide economyof scale and parallel processing advantages inherent in semiconductorprocesses. Furthermore, the generation of scrap separator membrane maybe minimized. Once separators have been cut, the oily process aid fluidmay be removed by a series of extraction steps with miscible solvents,the last extraction may be performed with a high-volatility solvent suchas isopropyl alcohol in some examples. Discrete separators, onceextracted, may be stored indefinitely in any suitable low-particleenvironment.

As previously mentioned polyolefin separator membranes may be inherentlyhydrophobic and may need to be made wettable to aqueous surfactants usedin the batteries of the present invention. One approach to make theseparator membranes wettable may be oxygen plasma treatment. Forexample, separators may be treated for 1 to 5 minutes in a 100 percentoxygen plasma at a wide variety of power settings and oxygen flow rates.While this approach may improve wettability for a time, it may bewell-known that plasma surface modifications provide a transient effectthat may not last long enough for robust wetting of electrolytesolutions. Another approach to improve wettability of separatormembranes may be to treat the surface by incorporating a suitablesurfactant on the membrane. In some cases, the surfactant may be used inconjunction with a hydrophilic polymeric coating that remains within thepores of the separator membrane.

Another approach to provide more permanence to the hydrophilicityimparted by an oxidative plasma treatment may be by subsequent treatmentwith a suitable hydrophilic organosilane. In this manner, the oxygenplasma may be used to activate and impart functional groups across theentire surface area of the microporous separator. The organosilane maythen covalently bond to and/or non-covalently adhere to the plasmatreated surface. In examples using an organosilane, the inherentporosity of the microporous separator may not be appreciably changed,monolayer surface coverage may also be possible and desired. Prior artmethods incorporating surfactants in conjunction with polymeric coatingsmay require stringent controls over the actual amount of coating appliedto the membrane, and may then be subject to process variability. Inextreme cases, pores of the separator may become blocked, therebyadversely affecting utility of the separator during the operation of theelectrochemical cell. An exemplary organosilane useful in the presentinvention may be (3-aminopropyl) triethoxysilane. Other hydrophilicorganosilanes may be known to those of skill in the art and may be usedwithout limitation.

Still another method for making separator membranes wettable by aqueouselectrolyte may be the incorporation of a suitable surfactant in theelectrolyte formulation. One consideration in the choice of surfactantfor making separator membranes wettable may be the effect that thesurfactant may have on the activity of one or more electrodes within theelectrochemical cell, for example, by increasing the electricalimpedance of the cell. In some cases, surfactants may have advantageousanti-corrosion properties, specifically in the case of zinc anodes inaqueous electrolytes. Zinc may be an example known to undergo a slowreaction with water to liberate hydrogen gas, which may be undesirable.Numerous surfactants may be known by those of skill in the art to limitrates of said reaction to advantageous levels. In other cases, thesurfactant may so strongly interact with the zinc electrode surface thatbattery performance may be impeded. Consequently, much care may need tobe made in the selection of appropriate surfactant types and loadinglevels to ensure that separator wettability may be obtained withoutdeleteriously affecting electrochemical performance of the cell. In somecases, a plurality of surfactants may be used, one being present toimpart wettability to the separator membrane and the other being presentto facilitate anti-corrosion properties to the zinc anode. In oneexample, no hydrophilic treatment is done to the separator membrane anda surfactant or plurality of surfactants is added to the electrolyteformulation in an amount sufficient to effect wettability of theseparator membrane.

Discrete separators may be integrated into the laminar microbattery bydirect placement into a means for storage including a designed cavity,pocket, or structure within the assembly. Desirably, this storage meansmay be formed by a laminar structure having a cutout, which may be ageometric offset of the separator shape, resulting in a cavity, pocket,or structure within the assembly. Furthermore, the storage means mayhave a ledge or step on which the separator rests during assembly. Theledge or step may optionally include a pressure-sensitive adhesive whichretains the discrete separator. Advantageously, the pressure-sensitiveadhesive may be the same one used in the construction and stack up ofother elements of an exemplary laminar microbattery.

Exemplary Illustrated Processing of Biocompatible Energization—PlacedSeparator

An example of the steps that may be involved in processing biocompatibleenergization elements may be found referring to FIGS. 4A-4N. Theprocessing at some of the exemplary steps may be found in the individualfigures. In FIG. 4A, a combination of a PET Cathode Spacer 401 and a PETGap Spacer 404 is illustrated. The PET Cathode Spacer 401 may be formedby applying films of PET 403 which, for example, may be approximately 3mils thick. On either side of the PET layer may be found PSA layers orthese may be capped with a PVDF release layer 402 which may beapproximately 1 mil in thickness. The PET Gap spacer 404 may be formedof a PVDF layer 409 which may be approximately 3 mils in thickness.There may be a capping PET layer 405 which may be approximately 0.5 milsin thickness. Between the PVDF layer 409 and the capping PET layer 405,in some examples, may be a layer of PSA.

Proceeding to FIG. 4B, a hole 406 in the PET Gap spacer layer 404 may becut by laser cutting treatment. Next at FIG. 4C, the cut PET Gap spacerlayer 404 may be laminated 408 to the PET Cathode Spacer layer 401.Proceeding to FIG. 4D, a cathode spacer hole 410 may be cut by lasercutting treatment. The alignment of this cutting step may be registeredto the previously cut features in the PET Gap spacer layer 404. At FIG.4E, a layer of Celgard 412, for an ultimate separator layer, may bebonded to a carrier 411. Proceeding to FIG. 4F, the Celgard material maybe cut to figures that are between the size of the previous two lasercut holes, and approximately the size of the hole 406 in the PET gapspacer, forming a precut separator 420. Proceeding to FIG. 4G, a pickand place tool 421 may be used to pick and place discrete pieces ofCelgard into their desired locations on the growing device. At FIG. 4H,the placed Celgard pieces 422 are fastened into place and then the PVDFrelease layer 423 may be removed. Proceeding to FIG. 4I, the growingdevice structure may be bonded to a film of the anode 425. The anode 425may comprise an anode collector film upon which a zinc anode film hasbeen electrodeposited.

Proceeding to FIG. 4J, a cathode slurry 430 may be placed into theformed gap. A squeegee 431 may be used in some examples to spread thecathode mix across a work piece and in the process fill the gaps of thebattery devices being formed. After filling, the remaining PVDF releaselayer 432 may be removed which may result in the structure illustratedin FIG. 4K. At FIG. 4L the entire structure may be subjected to a dryingprocess which may shrink the cathode slurry 440 to also be at the heightof the PET layer top. Proceeding to FIG. 4M, a cathode film layer 450,which may already have the cathode collector film upon it, may be bondedto the growing structure. In a final illustration at FIG. 4N a lasercutting process may be performed to remove side regions 460 and yield abattery element 470. There may be numerous alterations, deletions,changes to materials and thickness targets that may be useful within theintent of the present invention.

The result of the exemplary processing is depicted in some detail atFIG. 5. In an example, the following reference features may be defined.The cathode chemistry 510 may be located in contact with the cathode andcathode collector 520. A pressure-sensitive adhesive layer 530 may holdand seal the cathode collector 520 to a PET Spacer layer 540. On theother side of the PET Spacer layer 540, may be another PSA layer 550,which seals and adheres the PET Spacer layer 540 to the PET Gap layer560. Another PSA layer 565 may seal and adhere the PET Gap layer 560 tothe Anode and Anode Current Collector layers. A zinc Plated layer 570may be plated onto the Anode Current Collector 580. The separator layer590 may be located within the structure to perform the associatedfunctions as have been defined in the present invention. In someexamples, an electrolyte may be added during the processing of thedevice, in other examples, the separator may already includeelectrolyte.

Exemplary Processing Illustration of BiocompatibleEnergization—Deposited Separator

An example of the steps that may be involved in processing biocompatibleenergization elements is found in FIGS. 6A-6F. The processing at some ofthe exemplary steps may be found in the individual figures. There may benumerous alterations, deletions, changes to materials and thicknesstargets that may be useful within the intent of the present invention.

In FIG. 6A, a laminar construct 600 is illustrated. The laminarstructure may comprise two laminar construct release layers, 602 and 602a; two laminar construct adhesive layers 604 and 604 a, located betweenthe laminar construct release layers 602 and 602 a; and a laminarconstruct core 606, located between the two laminar construct adhesivelayers 604 and 604 a. The laminar construct release layers, 602 and 602a, and adhesive layers, 604 and 604 a, may be produced or purchased,such as a commercially available pressure-sensitive adhesive transfertape with primary liner layer. The laminar construct adhesive layers maybe a PVDF layer which may be approximately 1-3 millimeters in thicknessand cap the laminar construct core 606. The laminar construct core 606may comprise a thermoplastic polymer resin such as polyethyleneterephthalate, which, for example, may be approximately 3 millimetersthick. Proceeding to FIG. 6B, a means for storing the cathode mixture,such as a cavity for the cathode pocket 608, may be cut in the laminarconstruct by laser cutting treatment.

Next, at FIG. 6C, the bottom laminar construct release layer 602 a maybe removed from the laminar construct, exposing the laminar constructadhesive layer 604 a. The laminar construct adhesive layer 604 a maythen be used to adhere an anode connection foil 610 to cover the bottomopening of the cathode pocket 608. Proceeding to FIG. 6D, the anodeconnection foil 610 may be protected on the exposed bottom layer byadhering a masking layer 612. The masking layer 612 may be acommercially available PSA transfer tape with a primary liner. Next, atFIG. 6E, the anode connection foil 610 may be electroplated with acoherent metal 614, zinc, for example, which coats the exposed sectionof the anode connection foil 610 inside of the cathode pocket.Proceeding to 6F, the anode electrical collection masking layer 612 isremoved from the bottom of the anode connection foil 610 afterelectroplating.

FIGS. 7A-7F illustrate an alternate mode of processing the stepsillustrated in FIGS. 6A-6F. FIGS. 7A-7B may illustrate similar processesas depicted in FIGS. 6A-6B. The laminar structure may comprise twolaminar construct release layers, 702 and 702 a, one layer on eitherend; two laminar construct adhesive layers, 704 and 704 a, locatedbetween the laminar construct release layers 702 and 702 a; and alaminar construct core 706, located between the two laminar constructadhesive layers 704 and 704 a. The laminar construct release layers andadhesive layers may be produced or purchased, such as a commerciallyavailable pressure-sensitive adhesive transfer tape with primary linerlayer. The laminar construct adhesive layers may be a polyvinylidenefluoride (PVDF) layer which may be approximately 1-3 millimeters inthickness and cap the laminar construct core 706. The laminar constructcore 706 may comprise a thermoplastic polymer resin such as polyethyleneterephthalate, which, for example, may be approximately 3 millimetersthick. Proceeding to FIG. 7B, a storage means, such as a cavity, for thecathode pocket 708, may be cut in the laminar construct by laser cuttingtreatment. In FIG. 7C, an anode connection foil 710 may be obtained anda protective masking layer 712 applied to one side. Next, at FIG. 7D,the anode connection foil 710 may be electroplated with a layer 714 of acoherent metal, for example, zinc. Proceeding to FIG. 7E, the laminarconstructs of FIGS. 7B and 7D may be combined to form a new laminarconstruct as depicted in FIG. 7E by adhering the construct of FIG. 7B tothe electroplated layer 714 of FIG. 7D. The release layer 702 a of FIG.7B may be removed in order to expose adhesive layer 704 a of FIG. 7B foradherence onto electroplated layer 714 of FIG. 7D. Proceeding next toFIG. 7F, the anode protective masking layer 712 may be removed from thebottom of the anode connection foil 710.

FIGS. 8A-8H illustrate exemplary implementations of energizationelements to a biocompatible laminar structure, which at times isreferred to as a laminar assembly or a laminate assembly herein, similarto, for example, those illustrated in FIGS. 6A-6F and 7A-7F. Proceedingto FIG. 8A, a hydrogel separator precursor mixture 820 may be depositedon the surface of the laminate assembly. In some examples, as depicted,the hydrogel precursor mixture 820 may be applied up a release layer802. Next, at FIG. 8B, the hydrogel separator precursor mixture 820 maybe squeegeed 850 into the cathode pocket while being cleaned off of therelease layer 802. The term “squeegeed” may generally refer to the useof a planarizing or scraping tool to rub across the surface and movefluid material over the surface and into cavities as they exist. Theprocess of squeegeeing may be performed by equipment similar to thevernacular “Squeegee” type device or alternatively and planarizingdevice such as knife edges, razor edges and the like which may be madeof numerous materials as may be chemically consistent with the materialto be moved.

The processing depicted at FIG. 8B may be performed several times toensure coating of the cathode pocket, and increment the thickness ofresulting features. Next, at FIG. 8C, the hydrogel separator precursormixture may be allowed to dry in order to evaporate materials, which maytypically be solvents or diluents of various types, from the hydrogelseparator precursor mixture, and then the dispensed and appliedmaterials may be cured. It may be possible to repeat both of theprocesses depicted at FIG. 8B and FIG. 8C in combination in someexamples. In some examples, the hydrogel separator precursor mixture maybe cured by exposure to heat while in other examples the curing may beperformed by exposure to photon energy. In still further examples thecuring may involve both exposure to photon energy and to heat. There maybe numerous manners to cure the hydrogel separator precursor mixture.

The result of curing may be to form the hydrogel separator precursormaterial to the wall of the cavity as well as the surface region inproximity to an anode or cathode feature which in the present examplemay be an anode feature. Adherence of the material to the sidewalls ofthe cavity may be useful in the separation function of a separator. Theresult of curing may be to form an anhydrous polymerized precursormixture concentrate 822 which may be simply considered the separator ofthe cell. Proceeding to FIG. 8D, cathode slurry 830 may be depositedonto the surface of the laminar construct release layer 802. Next, atFIG. 8E the cathode slurry 830 may be squeegeed by device 850 into thecathode pocket and onto the anhydrous polymerized precursor mixtureconcentrate 822. The cathode slurry may be moved to its desired locationin the cavity while simultaneously being cleaned off to a large degreefrom the laminar construct release layer 802. The process of FIG. 8E maybe performed several times to ensure coating of the cathode slurry 830on top of the anhydrous polymerized precursor mixture concentrate 822.Next, at FIG. 8F, the cathode slurry may be allowed to dry down to forman isolated cathode fill 832 on top of the anhydrous polymerizedprecursor mixture concentrate 822, filling in the remainder of thecathode pocket.

Proceeding to FIG. 8G, an electrolyte formulation 840 may be added on tothe isolated cathode fill 832 and allowed to hydrate the isolatedcathode fill 832 and the anhydrous polymerized precursor mixtureconcentrate 822. Next, at FIG. 8H, a cathode connection foil 816 may beadhered to the remaining laminar construct adhesive layer 804 byremoving the remaining laminar construct release layer 802 and pressingthe connection foil 816 in place. The resulting placement may result incovering the hydrated cathode fill 842 as well as establishingelectrical contact to the cathode fill 842 as a cathode currentcollector and connection means.

FIGS. 9A through 9C illustrate an alternative example of the resultinglaminate assembly from FIG. 7D. In FIG. 9A, the anode connection foil710 may be obtained and a protective masking layer 712 applied to oneside. The anode connection foil 710 may be plated with a layer 714 ofcoherent metal with, for example, zinc. In similar fashion as describedin the previous figures. Proceeding to FIG. 9B, a hydrogel separator 910may be applied without the use of the squeegee method illustrated inFIG. 8E. The hydrogel separator precursor mixture may be applied invarious manners, for example, a preformed film of the mixture may beadhered by physical adherence; alternatively, a diluted mixture of thehydrogel separator precursor mixture may be dispensed and then adjustedto a desired thickness by the processing of spin coating. Alternativelythe material may be applied by spray coating, or any other processingequivalent. Next, at FIG. 9C, processing is depicted to create a segmentof the hydrogel separator that may function as a containment around aseparator region. The processing may create a region that limits theflow, or diffusion, of materials such as electrolyte outside theinternal structure of the formed battery elements. Such a blockingfeature 920 of various types may therefore be formed. The blockingfeature 920, in some examples, may correspond to a highly crosslinkedregion of the separator layer as may be formed in some examples byincreased exposure to photon energy in the desired region of theblocking feature 920. In other examples, materials may be added to thehydrogel separator material before it is cured to create regionallydifferentiated portions that upon curing become the blocking feature920. In still further examples, regions of the hydrogel separatormaterial may be removed either before or after curing by varioustechniques including, for example, chemical etching of the layer withmasking to define the regional extent. The region of removed materialmay create a blocking feature in its own right or alternatively,material may be added back into the void to create a blocking feature.The processing of the impermeable segment may occur through severalmethods including image out processing, increased crosslinking, heavyphotodosing, back-filling, or omission of hydrogel adherence to create avoid. In some examples, a laminate construct or assembly of the typedepicted as the result of the processing in FIG. 9C may be formedwithout the blocking feature 920.

Polymerized Battery Element Separators

In some battery designs, the use of a discrete separator (as describedin a previous section) may be precluded due to a variety of reasons suchas the cost, the availability of materials, the quality of materials, orthe complexity of processing for some material options as non-limitingexamples. In such cases, a cast or form-in-place separator which isillustrated in the processes of FIGS. 8A-8H, for example, may providedesirable benefits. While starch or pasted separators have been usedcommercially with success in AA and other Leclanché format orzinc-carbon batteries, such separators may be unsuitable in some waysfor use in certain examples of laminar microbatteries. Particularattention may need to be paid to the uniformity and consistency ofgeometry for any separator used in the batteries of the presentinvention. Precise control over separator volume may be needed tofacilitate precise subsequent incorporation of known cathode volumes andsubsequent realization of consistent discharge capacities and cellperformance.

A method to achieve a uniform, mechanically robust form-in-placeseparator may be to use UV-curable hydrogel formulations. Numerouswater-permeable hydrogel formulations may be known in variousindustries, for example, the contact lens industry. An example of acommon hydrogel in the contact lens industry may bepoly(hydroxyethylmethacrylate) crosslinked gel, or simply pHEMA. Fornumerous applications of the present invention, pHEMA may possess manyattractive properties for use in Leclanché and zinc-carbon batteries.pHEMA typically may maintain a water content of approximately 30-40percent in the hydrated state while maintaining an elastic modulus ofabout 100 psi or greater. Furthermore, the modulus and water contentproperties of crosslinked hydrogels may be adjusted by one of ordinaryskill in the art by incorporating additional hydrophilic monomeric (e.g.methacrylic acid) or polymeric (e.g. polyvinylpyrrolidone) components.In this manner, the water content, or more specifically, the ionicpermeability of the hydrogel may be adjusted by formulation.

Of particular advantage in some examples, a castable and polymerizablehydrogel formulation may comprise one or more diluents to facilitateprocessing. The diluent may be chosen to be volatile such that thecastable mixture may be squeegeed into a cavity, and then allowed asufficient drying time to remove the volatile solvent component. Afterdrying, a bulk photopolymerization may be initiated by exposure toactinic radiation of appropriate wavelength, such as blue UV light at420 nm, for the chosen photoinitiator, such as CGI 819. The volatilediluent may help to provide a desirable application viscosity so as tofacilitate casting a uniform layer of polymerizable material in thecavity. The volatile diluent may also provide beneficial surface tensionlowering effects, particularly in the case where strongly polar monomersare incorporated in the formulation. Another aspect that may beimportant to achieve the casting of a uniform layer of polymerizablematerial in the cavity may be the application viscosity. Common smallmolar mass reactive monomers typically do not have very highviscosities, which may be typically only a few centipoise. In an effortto provide beneficial viscosity control of the castable andpolymerizable separator material, a high molar mass polymeric componentknown to be compatible with the polymerizable material may be selectedfor incorporation into the formulation. Examples of high molar masspolymers which may be suitable for incorporation into exemplaryformulations may include polyvinylpyrrolidone and polyethylene oxide.

In some examples the castable, polymerizable separator may beadvantageously applied into a designed cavity, as previously described.In alternative examples, there may be no cavity at the time ofpolymerization. Instead, the castable, polymerizable separatorformulation may be coated onto an electrode-containing substrate, forexample, patterned zinc plated brass, and then subsequently exposed toactinic radiation using a photomask to selectively polymerize theseparator material in targeted areas. Unreacted separator material maythen be removed by exposure to appropriate rinsing solvents. In theseexamples, the separator material may be designated as aphoto-patternable separator.

Multiple Component Separator Formulations

The separator, useful according to examples of the present invention,may have a number of properties that may be important to its function.In some examples, the separator may desirably be formed in such a manneras to create a physical barrier such that layers on either side of theseparator do not physically contact one another. The layer may thereforehave an important characteristic of uniform thickness, since while athin layer may be desirable for numerous reasons, a void or gap freelayer may be essential. Additionally, the thin layer may desirably havea high permeability to allow for the free flow of ions. Also, theseparator requires optimal water uptake to optimize mechanicalproperties of the separator. Thus, the formulation may include acrosslinking component, a hydrophilic polymer component, and a solventcomponent.

A crosslinker may be a monomer with two or more polymerizable doublebonds. Suitable crosslinkers may be compounds with two or morepolymerizable functional groups. Examples of suitable hydrophiliccrosslinkers may also include compounds having two or more polymerizablefunctional groups, as well as hydrophilic functional groups such aspolyether, amide or hydroxyl groups. Specific examples may includeTEGDMA (tetraethyleneglycol dimethacrylate), TrEGDMA (triethyleneglycoldimethacrylate), ethyleneglycol dimethacylate (EGDMA), ethylenediaminedimethylacrylamide, glycerol dimethacrylate and/or combinations thereof.

The amounts of crosslinker that may be used in some examples may range,e.g., from about 0.000415 to about 0.0156 mole per 100 grams of reactivecomponents in the reaction mixture. The amount of hydrophiliccrosslinker used may generally be about 0 to about 2 weight percent and,for example, from about 0.5 to about 2 weight percent. Hydrophilicpolymer components capable of increasing the viscosity of the reactivemixture and/or increasing the degree of hydrogen bonding with theslow-reacting hydrophilic monomer, such as high molecular weighthydrophilic polymers, may be desirable.

The high molecular weight hydrophilic polymers provide improvedwettability, and in some examples may improve wettability to theseparator of the present invention. In some non-limiting examples, highmolecular weight hydrophilic polymers may be hydrogen bond receiverswhich in aqueous environments, hydrogen bond to water, thus becomingeffectively more hydrophilic. The absence of water may facilitate theincorporation of the hydrophilic polymer in the reaction mixture. Asidefrom the specifically named high molecular weight hydrophilic polymers,it may be expected that any high molecular weight polymer will be usefulin the present invention provided that when the polymer is added to anexemplary silicone hydrogel formulation, the hydrophilic polymer (a)does not substantially phase separate from the reaction mixture and (b)imparts wettability to the resulting cured polymer.

In some examples, the high molecular weight hydrophilic polymer may besoluble in the diluent at processing temperatures. Manufacturingprocesses which use water or water soluble diluents, such as isopropylalcohol (IPA), may be desirable examples due to their simplicity andreduced cost. In these examples, high molecular weight hydrophilicpolymers which are water soluble at processing temperatures may also bedesirable examples.

Examples of high molecular weight hydrophilic polymers may include butare not limited to polyamides, polylactones, polyimides, polylactams andfunctionalized polyamides, polylactones, polyimides, polylactams, suchas PVP and copolymers thereof, or alternatively, DMA functionalized bycopolymerizing DMA with a lesser molar amount of a hydroxyl-functionalmonomer such as HEMA, and then reacting the hydroxyl groups of theresulting copolymer with materials containing radical polymerizablegroups. High molecular weight hydrophilic polymers may include but arenot limited to poly-N-vinyl pyrrolidone, poly-N-vinyl-2-piperidone,poly-N-vinyl-2-caprolactam, poly-N-vinyl-3-methyl-2-caprolactam,poly-N-vinyl-3-methyl-2-piperidone, poly-N-vinyl-4-methyl-2-piperidone,poly-N-vinyl-4-methyl-2-caprolactam, poly-N-vinyl-3-ethyl-2-pyrrolidone,and poly-N-vinyl-4,5-dimethyl-2-pyrrolidone, polyvinylimidazole,poly-N—N-dimethylacrylamide, polyvinyl alcohol, polyacrylic acid,polyethylene oxide, poly 2 ethyl oxazoline, heparin polysaccharides,polysaccharides, mixtures and copolymers (including block or random,branched, multichain, comb-shaped or star-shaped) thereof wherepoly-N-vinylpyrrolidone (PVP) may be a desirable example where PVP hasbeen added to a hydrogel composition to form an interpenetrating networkwhich shows a low degree of surface friction and a low dehydration rate.

Additional components or additives, which may generally be known in theart, may also be included. Additives may include but are not limited toultra-violet absorbing compounds, photo-initiators such as CGI 819,reactive tints, antimicrobial compounds, pigments, photochromic, releaseagents, combinations thereof and the like.

The method associated with these types of separators may also includereceiving CGI 819; then mixing with PVP, HEMA, EGDMA and IPA; and thencuring the resulting mixture with a heat source or an exposure tophotons. In some examples the exposure to photons may occur where thephotons' energy is consistent with a wavelength occurring in theultraviolet portion of the electromagnetic spectrum. Other methods ofinitiating polymerization generally performed in polymerizationreactions are within the scope of the present invention.

Current Collectors and Electrodes

In some examples of zinc carbon and Leclanche cells, the cathode currentcollector may be a sintered carbon rod. This type of material may facetechnical hurdles for thin electrochemical cells of the presentinvention. In some examples, printed carbon inks may be used in thinelectrochemical cells to replace a sintered carbon rod for the cathodecurrent collector, and in these examples, the resulting device may beformed without significant impairment to the resulting electrochemicalcell. Typically, the carbon inks may be applied directly to packagingmaterials which may comprise polymer films, or in some cases metalfoils. In the examples where the packaging film may be a metal foil, thecarbon ink may need to protect the underlying metal foil from chemicaldegradation and/or corrosion by the electrolyte. Furthermore, in theseexamples, the carbon ink current collector may need to provideelectrical conductivity from the inside of the electrochemical cell tothe outside of the electrochemical cell, implying sealing around orthrough the carbon ink. Due to the porous nature of carbon inks, thismay be not easily accomplished without significant challenges. Carboninks also may be applied in layers that have finite and relatively smallthickness, for example, 10 to 20 microns. In a thin electrochemical celldesign in which the total internal package thickness may only be about100 to 150 microns, the thickness of a carbon ink layer may take up asignificant fraction of the total internal volume of the electrochemicalcell, thereby negatively impacting electrical performance of the cell.Further, the thin nature of the overall battery and the currentcollector in particular may imply a small cross-sectional area for thecurrent collector. As resistance of a trace increases with trace length,and decreases with cross-sectional area, there may be a direct tradeoffbetween current collector thickness and resistance. The bulk resistivityof carbon ink may be insufficient to meet the resistance requirement ofthin batteries. Inks filled with silver or other conductive metals mayalso be considered to decrease resistance and/or thickness, but they mayintroduce new challenges such as incompatibility with novelelectrolytes. In consideration of these factors, in some examples it maybe desirable to realize efficient and high performance thinelectrochemical cells of the present invention by utilizing a thin metalfoil as the current collector, or to apply a thin metal film to anunderlying polymer packaging layer to act as the current collector. Suchmetal foils may have significantly lower resistivity, thereby allowingthem to meet electrical resistance requirements with much less thicknessthan printed carbon inks.

In some examples, one or more of the top and/or bottom packaging layersmay serve as a substrate for a sputtered current collector metal ormetal stack. For example, 3M® Scotchpak 1109 backing may be metallizedusing physical vapor deposition (PVD) of one or more metallic layersuseful as a current collector for a cathode. Exemplary metal stacksuseful as cathode current collectors may be Ti—W (titanium-tungsten)adhesion layers and Ti (titanium) conductor layers. Exemplary metalstacks useful as anode current collectors may be Ti—W adhesion layers,Au (gold) conductor layers, and In (indium) deposition layers. Thethickness of the PVD layers may be less than 500 nm in total. Ifmultiple layers of metals are used, the electrochemical and barrierproperties may need to be compatible with the battery. For example,copper may be electroplated on top of a seed layer to grow a thick layerof conductor. Additional layers may be plated upon the copper. However,copper may be electrochemically incompatible with certain electrolytesespecially in the presence of zinc. Accordingly, if copper is used as alayer in the battery, it may need to be sufficiently isolated from thebattery electrolyte. Alternatively, copper may be excluded or anothermetal substituted.

In some other examples, top and/or bottom packaging foils may alsofunction as current collectors. For example, a 25 micron brass foil maybe useful as an anode current collector for a zinc anode. The brass foilmay be optionally electroplated with indium prior to electroplating withzinc. In one example, cathode current collector packaging foils maycomprise titanium foil, Hastelloy C-276 foil, chromium foil, and/ortantalum foil. In certain designs, one or more packaging foils may befine blanked, embossed, etched, textured, laser machined, or otherwiseprocessed to provide desirable form, surface roughness, and/or geometryto the final cell packaging.

Anode and Anode Corrosion Inhibitors

The anode for the laminar battery of the present invention may, forexample, comprise zinc. In traditional zinc carbon batteries, a zincanode may take the physical form of a can in which the contents of theelectrochemical cell may be contained. For the battery of the presentinvention, a zinc can may be an example but there may be other physicalforms of zinc that may provide desirable to realize ultra-small batterydesigns.

Electroplated zinc may have examples of use in a number of industries,for example, for the protective or aesthetic coating of metal parts. Insome examples, electroplated zinc may be used to form thin and conformalanodes useful for batteries of the present invention.

Furthermore, the electroplated zinc may be patterned in seeminglyendless configurations, depending on the design intent. A facile meansfor patterning electroplated zinc may be processing with the use of aphotomask or a physical mask. A plating mask may be fabricated by avariety of approaches. One approach may be by using a photomask. Inthese examples, a photoresist may be applied to a conductive substrate,the substrate on which zinc may subsequently be plated. The desiredplating pattern may be then projected to the photoresist by means of aphotomask, thereby causing curing of selected areas of photoresist. Theuncured photoresist may then be removed with appropriate solvent andcleaning techniques. The result may be a patterned area of conductivematerial that may receive an electroplated zinc treatment. While thismethod may provide benefit to the shape or design of the zinc to beplated, the approach may require use of available photopatternablematerials, which may have constrained properties to the overall cellpackage construction. Consequently, new and novel methods for patterningzinc may be required to realize some designs of thin microbatteries ofthe present invention.

An alternative means of patterning zinc anodes may be by means of aphysical mask application. A physical mask may be made by cuttingdesirable apertures in a film having desirable barrier and/or packagingproperties. Additionally, the film may have pressure sensitive adhesiveapplied to one or both sides. Finally, the film may have protectiverelease liners applied to one or both adhesives. The release liner mayserve the dual purpose of protecting the adhesive during aperturecutting and protecting the adhesive during specific processing steps ofassembling the electrochemical cell, specifically the cathode fillingstep, described in following description. In some examples, a zinc maskmay comprise a PET film of approximately 100 microns thickness to whicha pressure sensitive adhesive may be applied to both sides in a layerthickness of approximately 10-20 microns. Both PSA layers may be coveredby a PET release film which may have a low surface energy surfacetreatment, and may have an approximate thickness of 50 microns. In theseexamples, the multi-layer zinc mask may comprise PSA and PET film. PETfilms and PET/PSA zinc mask constructs as described herein may bedesirably processed with precision nanosecond laser micromachiningequipment, such as, an Oxford Lasers E-Series laser micromachiningworkstation, to create ultra-precise apertures in the mask to facilitatelater plating. In essence, once the zinc mask has been fabricated, oneside of the release liner may be removed, and the mask with aperturesmay be laminated to the anode current collector and/or anode-sidepackaging film/foil. In this manner, the PSA creates a seal at theinside edges of the apertures, facilitating clean and precise masking ofthe zinc during electroplating.

The zinc mask may be placed and then electroplating of one or moremetallic materials may be performed. In some examples, zinc may beelectroplated directly onto an electrochemically compatible anodecurrent collector foil such as brass. In alternate design examples wherethe anode side packaging comprises a polymer film or multi-layer polymerfilm upon which seed metallization has been applied, zinc, and/or theplating solutions used for depositing zinc, may not be chemicallycompatible with the underlying seed metallization. Manifestations oflack of compatibility may include film cracking, corrosion, and/orexacerbated H₂ evolution upon contact with cell electrolyte. In such acase, additional metals may be applied to the seed metal to affectbetter overall chemical compatibility in the system. One metal that mayfind particular utility in electrochemical cell constructions may beindium. Indium may be widely used as an alloying agent in battery gradezinc with its primary function being to provide an anti-corrosionproperty to the zinc in the presence of electrolyte. In some examples,indium may be successfully deposited on various seed metallizations suchas Ti—W and Au. Resulting films of 1-3 microns of indium on the seedmetallization layers may be low-stress and adherent. In this manner, theanode-side packaging film and attached current collector having anindium top layer may be conformable and durable. In some examples, itmay be possible to deposit zinc on an indium-treated surface, theresulting deposit may be very non-uniform and nodular. This effect mayoccur at lower current density settings, for example, 20 ASF. As viewedunder a microscope, nodules of zinc may be observed to form on theunderlying smooth indium deposit. In certain electrochemical celldesigns, the vertical space allowance for the zinc anode layer may be upto about 5-10 microns maximum, but in some examples, lower currentdensities may be used for zinc plating, and the resulting nodulargrowths may grow taller than the maximum anode vertical allowance. Itmay be that the nodular zinc growth stems from a combination of the highoverpotential of indium and the presence of an oxide layer of indium.

In some examples, higher current density DC plating may overcome therelatively large nodular growth patterns of zinc on indium surfaces. Forexample, 100 ASF plating conditions may result in nodular zinc, but thesize of the zinc nodules may be drastically reduced compared to 20 ASFplating conditions. Furthermore, the number of nodules may be vastlygreater under 100 ASF plating conditions. The resulting zinc film mayultimately coalesce to a more or less uniform layer with only someresidual feature of nodular growth while meeting the vertical spaceallowance of about 5-10 microns.

An added benefit of indium in the electrochemical cell may be reductionof H₂ formation, which may be a slow process that occurs in aqueouselectrochemical cells containing zinc. The indium may be beneficiallyapplied to one or more of the anode current collector, the anode itselfas a co-plated alloying component, or as a surface coating on theelectroplated zinc. For the latter case, indium surface coatings may bedesirably applied in-situ by way of an electrolyte additive such asindium trichloride, indium sulfate or indium acetate. When suchadditives may be added to the electrolyte in small concentrations,indium may spontaneously plate on exposed zinc surfaces as well asportions of exposed anode current collector.

Zinc and similar anodes commonly used in commercial primary batteries istypically found in sheet, rod, and paste forms. The anode of aminiature, biocompatible battery may be of similar form, e.g. thin foil,or may be plated as previously mentioned. The properties of this anodemay differ significantly from those in existing batteries, for example,because of differences in contaminants or surface finish attributed tomachining and plating processes. Accordingly, the electrodes andelectrolyte may require special engineering to meet capacity, impedance,and shelf life requirements. For example, special plating processparameters, plating bath composition, surface treatment, and electrolytecomposition may be needed to optimize electrode performance.

Cathode Mixture

There are numerous cathode chemistry mixtures that may be consistentwith the concepts of the present invention. In some examples, a cathodemixture, which may be a term for a chemical formulation used to form abattery's cathode, may be applied as a paste, gel, suspension, orslurry, and may comprise a transition metal oxide such as manganesedioxide, some form of conductive additive which, for example, may be aform of conductive powder such as carbon black or graphite, and awater-soluble polymer such as polyvinylpyrrolidone (PVP) or some otherbinder additive. In some examples, other components may be included suchas one or more of binders, electrolyte salts, corrosion inhibitors,water or other solvents, surfactants, rheology modifiers, and otherconductive additives, such as, conductive polymers. Once formulated andappropriately mixed, the cathode mixture may have a desirable rheologythat allows it to either be dispensed onto desired portions of theseparator and/or cathode current collector, or squeegeed through ascreen or stencil in a similar manner. In some examples, the cathodemixture may be dried before being used in later cell assembly steps,while in other examples, the cathode may contain some or all of theelectrolyte components, and may only be partially dried to a selectedmoisture content.

The transition metal oxide may, for example, be manganese dioxide. Themanganese dioxide which may be used in the cathode mixture may be, forexample, electrolytic manganese dioxide (EMD) due to the beneficialadditional specific energy that this type of manganese dioxide providesrelative to other forms, such as natural manganese dioxide (NMD) orchemical manganese dioxide (CMD). Furthermore, the EMD useful inbatteries of the present invention may need to have a particle size andparticle size distribution that may be conducive to the formation ofdepositable or printable cathode mixture pastes/slurries. Specifically,the EMD may be processed to remove significant large particulatecomponents that may be considered large relative to other features suchas battery internal dimensions, separator thicknesses, dispense tipdiameters, stencil opening sizes, or screen mesh sizes. Particle sizeoptimization may also be used to improve performance of the battery, forexample, internal impedance and discharge capacity.

Milling is the reduction of solid materials from one average particlesize to a smaller average particle size, by crushing, grinding, cutting,vibrating, or other processes. Milling may also be used to free usefulmaterials from matrix materials in which they may be embedded, and toconcentrate minerals. A mill is a device that breaks solid materialsinto smaller pieces by grinding, crushing, or cutting. There may beseveral means for milling and many types of materials processed in them.Such means of milling may include: ball mill, bead mill, mortar andpestle, roller press, and jet mill among other milling alternatives. Oneexample of milling that may be utilized in the present invention is jetmilling. After the milling, the state of the solid is changed, forexample, the particle size, the particle size disposition and theparticle shape. Aggregate milling processes may also be used to removeor separate contamination or moisture from aggregate to produce “dryfills” prior to transport or structural filling. Some equipment maycombine various techniques to sort a solid material into a mixture ofparticles whose size is bounded by both a minimum and maximum particlesize. Such processing may be referred to as “classifiers” or“classification.”

Milling may be one aspect of cathode mixture production for uniformparticle size distribution of the cathode mixture ingredients. Uniformparticle size in a cathode mixture may assist in viscosity, rheology,electroconductivity, and other properties of a cathode. Milling mayassist these properties by controlling agglomeration, or a masscollection, of the cathode mixture ingredients. Agglomeration—theclustering of disparate elements, which in the case of the cathodemixture, may be carbon allotropes and transition metal oxides—maynegatively affect the filling process by leaving voids in the desiredcathode cavity as illustrated in FIG. 11 and described subsequently.

Also, filtration may be another important step for the removal ofagglomerated or unwanted particles. Unwanted particles may includeover-sized particles, contaminates, or other particles not explicitlyaccounted for in the preparation process. Filtration may be accomplishedby means such as filter-paper filtration, vacuum filtration,chromatography, microfiltration, and other means of filtration.

In some examples, EMD may have an average particle size of 7 micronswith a large particle content that may contain particulates up to about70 microns. In alternative examples, the EMD may be sieved, furthermilled, or otherwise separated or processed to limit large particulatecontent to below a certain threshold, for example, 25 microns orsmaller.

The cathode may also comprise silver dioxide or nickel oxyhydroxide.Such materials may offer increased capacity and less decrease in loadedvoltage during discharge relative to manganese dioxide, both desirableproperties in a battery. Batteries based on these cathodes may havecurrent examples present in industry and literature. A novelmicrobattery utilizing a silver dioxide cathode may include abiocompatible electrolyte, for example, one comprising zinc chlorideand/or ammonium chloride instead of potassium hydroxide.

Some examples of the cathode mixture may include a polymeric binder. Thebinder may serve a number of functions in the cathode mixture. Theprimary function of the binder may be to create a sufficientinter-particle electrical network between EMD particles and carbonparticles. A secondary function of the binder may be to facilitatemechanical adhesion and electrical contact to the cathode currentcollector. A third function of the binder may be to influence therheological properties of the cathode mixture for advantageousdispensing and/or stenciling/screening. Still, a fourth function of thebinder may be to enhance the electrolyte uptake and distribution withinthe cathode.

The choice of the binder polymer as well as the amount to be used may bebeneficial to the function of the cathode in the electrochemical cell ofthe present invention. If the binder polymer is too soluble in theelectrolyte to be used, then the primary function of thebinder—electrical continuity—may be drastically impacted to the point ofcell non-functionality. On the contrary, if the binder polymer isinsoluble in the electrolyte to be used, portions of EMD may beionically insulated from the electrolyte, resulting in diminished cellperformance such as reduced capacity, lower open circuit voltage, and/orincreased internal resistance.

The binder may be hydrophobic; it may also be hydrophilic. Examples ofbinder polymers useful for the present invention comprise PVP,polyisobutylene (PIB), rubbery triblock copolymers comprising styreneend blocks such as those manufactured by Kraton Polymers,styrene-butadiene latex block copolymers, polyacrylic acid,hydroxyethylcellulose, carboxymethylcellulose, fluorocarbon solids suchas polytetrafluoroethylene, among others.

A solvent may be one component of the cathode mixture. A solvent may beuseful in wetting the cathode mixture, which may assist in the particledistribution of the mixture. One example of a solvent may be toluene.Also, a surfactant may be useful in wetting, and thus distribution, ofthe cathode mixture. One example of a surfactant may be a detergent,such as Triton™ QS-44. Triton™ QS-44 may assist in the dissociation ofaggregated ingredients in the cathode mixture, allowing for a moreuniform distribution of the cathode mixture ingredients.

A conductive carbon may typically be used in the production of acathode. Carbon is capable of forming many allotropes, or differentstructural modifications. Different carbon allotropes have differentphysical properties allowing for variation in electroconductivity. Forexample, the “springiness” of carbon black may help with adherence of acathode mixture to a current collector. However, in energizationelements requiring relatively low amounts of energy, these variations inelectroconductivity may be less important than other favorableproperties such as density, particle size, heat conductivity, andrelative uniformity, among other properties. Examples of carbonallotropes include: diamond, graphite, graphene, amorphous carbon(informally called carbon black), buckminsterfullerenes, glassy carbon(also called vitreous carbon), carbon aerogels, and other possible formsof carbon capable of conducting electricity. One example of a carbonallotrope may be graphite.

One example of a completed cathode mixture formulation may be given inTable 1 below:

TABLE 1 Formulation Example Relative weight 80:20 JMEMD/KS6 4.900 PIBB10 (from 20% solution) 0.100 toluene 2.980 Total 7.980where PIB is polyisobutylene, JMEMD is jet milled manganese dioxide, KS6is a graphite produced by Timcal, and PIB B10 is polyisobutylene with amolecular weight grade of B10.

Once the cathode mixture has been formulated and processed, the mixturemay be dispensed, applied, and/or stored onto a surface such as thehydrogel separator, or the cathode current collector, or into a volumesuch as the cavity in the laminar structure. Filing onto a surface mayresult in a volume being filled over time. In order to apply, dispense,and/or store the mixture, a certain rheology may be desired to optimizethe dispensing, applying, and/or storing process. For example, a lessviscous rheology may allow for better filling of the cavity while at thesame time possibly sacrificing particle distribution. A more viscousrheology may allow for optimized particle distribution, while possiblydecreasing the ability to fill the cavity and possibly losingelectroconductivity.

For example, FIGS. 10A-10F illustrate optimized and non-optimizeddispensing or application into a cavity. FIG. 10A illustrates a cavityoptimally filled with the cathode mixture after application, dispensing,and/or storing. FIG. 10B illustrates a cavity with insufficient fillingin the bottom left quadrant 1002, which may be a direct result ofundesirable cathode mixture rheology. FIG. 10C illustrates a cavity withinsufficient filling in the top right quadrant 1004, which may be adirect result of undesirable cathode mixture rheology. FIGS. 10D and 10Eillustrate a cavity with insufficient filling in the middle 1006 orbottom 1008 of the cavity, which may be a bubble caused by a directresult of undesirable cathode mixture rheology. FIG. 10F illustrates acavity with insufficient filling towards the top 1010 of the cavity,which may be a direct result of undesirable cathode mixture rheology.The defects illustrated in FIGS. 10B-10F may result in several batteryissues, for example, reduced capacity, increased internal resistance,and degraded reliability.

Further, in FIG. 11, agglomeration 1102 may occur as a result ofundesirable cathode mixture rheology. Agglomeration may result indecreased performance of the cathode mixture, for example, decreaseddischarge capacity and increased internal resistance.

In one example, the cathode mixture may resemble a peanut-butter likeconsistency optimized for squeegee filling the laminar construct cavitywhile maintaining electroconductivity. In another example, the mixturemay be viscous enough to be printed into the cavity. While in yetanother example, the cathode mixture may be dried, placed, and stored inthe cavity.

Electrolyte

An electrolyte is a component of a battery which facilitates a chemicalreaction to take place between the chemical materials of the electrodes.Typical electrolytes may be electrochemically active to the electrodes,for example, allowing oxidation and reduction reactions to occur. Asused herein, an electrolyte may be a solution comprising a suitablesolvent and ionic species. The solution may be suitable in that thesolution may support the presence of these ionic species. An ionizingsolute may be a material that when added to the solvent dissolves intosolvated ionic species. In some examples, the ionizing solute may be anionizing salt. The electrolyte solutions that contain ionic species mayhave an ability to support electrical conductivity by the diffusion ofthe ionic species in the solution.

In some examples, this important electrochemical activity may make for achallenge to creating devices that are biocompatible. For example,potassium hydroxide (KOH) is a commonly used electrolyte in alkalinecells. At high concentration the material has a high pH and may interactunfavorably with various living tissues. On the other hand, in someexamples, electrolytes may be employed which may be lesselectrochemically active; however, these materials may typically resultin reduced electrical performance, such as reduced cell voltage andincreased cell resistance. Accordingly, one key aspect of the design andengineering of a biomedical microbattery may be the electrolyte. It maybe desirable for the electrolyte to be sufficiently active to meetelectrical requirements while also being relatively safe for use in- oron-body.

Various test scenarios may be used to determine the safety profile ofbattery components, such as electrolytes, to living cells. Theseresults, in conjunction with tests of the battery packaging, may allowengineering design of a battery system that may meet requirements. Forexample, when developing a powered contact lens, battery electrolytesmay be tested on a human corneal cell model. These tests may includeexperiments on electrolyte concentration, exposure time, and additives.The results of such tests may indicate cell metabolism and otherphysiological aspects.

Electrolytes for use in the present invention may include zinc chloride,zinc acetate, zinc sulfate, zinc bromide, zinc gluconate hydrate, zincnitrate, and zinc iodide, ammonium acetate, and ammonium chloride inmass concentrations from approximately 0.1 percent to 50 percent, and ina non-limiting example may be approximately 25 percent. The specificconcentrations may depend on solubility, electrochemical activity,battery performance, shelf life, seal integrity, and biocompatibilityamongst other dependencies. In some examples, several classes ofadditives may be utilized in the composition of a battery system.Additives may be mixed into the base electrolyte formulation to alterits characteristics. For example, gelling agents such as agar may reducethe ability of the electrolyte to leak out of packing, therebyincreasing safety. Other examples may include carboxymethyl cellulose orcellulose gum. Other examples may include hydroxypropyl methylcellulose. Corrosion inhibitors such as indium acetate may be added tothe electrolyte, for example, to improve shelf life by reducing theundesired dissolution of electrode material such as the zinc anode intothe electrolyte. These inhibitors may positively or adversely affect thesafety profile of the battery. Wetting agents or surfactants may beadded, for example, to allow the electrolyte to wet the separator or tobe filled into the battery package. Again, these wetting agents may bepositive or negative for safety. The addition of surfactant to theelectrolyte may increase the electrical impedance of the cell.Accordingly, the lowest concentration of surfactant to achieve thedesired wetting or other properties may be desired. Exemplarysurfactants may include Triton™ X-100, Triton™ QS44, and Dowfax™ 3B2 inconcentrations from 0.01 percent to 2 percent. One exemplary electrolyteformulation may comprise approximately 10 to 20 percent ZnCl₂,approximately 250 to 500 ppm Triton™ QS44, approximately 100 to 200 ppmindium +3 ion supplied as indium acetate, and the balance comprisingwater.

Novel electrolytes are also emerging which may dramatically improve thesafety profile of biomedical microbatteries. For example, a class ofsolid electrolytes may be inherently resistant to leaking while stilloffering suitable electrical performance. A gelled or hydro-gelledelectrolyte may also provide adequate electrical performance whilemaintaining resilience to leaking and thus preserving biocompatibility.A gelled electrolyte may also replace the need of a battery separatorwhere the gelled electrolyte's permeability properties may also functionto prevent an electrical short between the electrodes. For example,flexible asymmetric supercapacitors using ultrathin two-dimensional MnO₂nano-sheets and graphene in aqueous Ca(NO₃)₂—SiO₂ gel electrolyte haverealized excellent electrochemical performance (such as energy densityup to 97.2 Wh kg⁻¹, much higher than traditional MnO₂ basedsupercapacitors and no more than 3% capacitance loss even after 10,000cycles) while maintaining biocompatibility.

These types of gelled electrolytes may be formulated by, for example,creating an aqueous solution of 2 molar calcium nitrate (Ca(NO₃)₂) indeionized water, adding 1 percent weight by weightcarboxymethylcellulose (CMC), adding 10 percent weight by weight silicondioxide (SiO₂), mixing to homogeny, then letting sit until gelled.

FIGS. 12A-F illustrate the exemplary use of a gelled electrolyte in abiocompatible energization element. In FIG. 12A, a pick and place tool1221 may be used to pick and place a cut or pre-formed piece of a gelledelectrolyte into a desired locations on the energization element. AtFIG. 12B, the placed gelled electrolyte piece 1222 may be fastened intoplace and then the PVDF release layer 1223 may be removed. Proceeding toFIG. 12C, the growing device structure may be bonded to a film of theanode 1225. The anode 1225 may comprise an anode collector film uponwhich a zinc anode film has been electrodeposited.

Proceeding to FIG. 12D, a cathode slurry 1230 may be placed into theformed gap. A squeegee 1231 may be used in some examples to spread thecathode mix across a work piece and in the process fill the gaps of thebattery devices being formed. After filling, the remaining PVDF releaselayer 1232 may be removed which may result in the structure illustratedin FIG. 12E. At FIG. 12F the entire structure may be subjected to adrying process which may shrink the cathode slurry 1240 to also be atthe height of the PET layer top. There may be numerous alterations,deletions, changes to materials and thickness targets that may be usefulwithin the intent of the present invention.

Reserve Cells

Reserve cells are batteries in which the active materials, theelectrodes and electrolyte, are separated until the time of use. Becauseof this separation, the cells' self-discharge is greatly reduced andshelf life is greatly increased. As an example batteries using “saltwater” electrolyte are commonly used in reserve cells for marine use.Torpedoes, buoys, and emergency lights may use such batteries. Saltwater batteries may be designed from a variety of electrode materials,including zinc, magnesium, aluminum, copper, tin, manganese dioxide, andsilver oxide. The electrolyte may be actual sea water, for example,water from the ocean flooding the battery upon contact, or may be aspecially engineered saline formulation.

In other examples, a reserve cell may be formulated from any of theelectrolyte formulations as have been discussed herein, wherein theelectrolyte is segregated from the battery cell by a storage means. Insome examples, a physical action such as applying force upon the storagemeans may rupture the storage device in a planned manner such that theelectrolyte flows into the battery cell and activates the potential forthe chemicals of the electrodes to be turned into electrical energy. Insome other examples, a seal of the storage means may be electricallyactivated. For example, the application of an electric potential on athin metal seal may melt the seal allowing electrolyte to escape thestorage means. In still further examples, an electrically activated poremay be utilized to allow the electrolyte to be released from its storagemeans. For these examples, there typically may be a source ofelectricity to activate the flow of electrolyte into the primarybattery. An inductive energy source or a photoactive energy (i.e.photocell) source may allow for a controlled signal to provideelectrical energy to release electrolyte.

A second reserve cell may also be ideal for this purpose of activatingflow of electrolyte into a primary battery on receipt of a signal. Thesecond reserve cell may be a smaller cell that allows for fluid from itssurroundings to diffuse into the cell. After the second reserve cellbattery device is formed without electrolyte the shelf life may beextended. After the battery device is formed into a biomedical devicesuch as a contact lens it may then be stored in a saline solution. Thissaline solution may diffuse into the battery thus activating the secondreserve cell. A subsequent activation signal, such as the presence oflight after a package containing the contact lens is opened may activatethe main (reserve) sell to allow electrolyte to flow into the batterydevice and activate the battery.

A saline electrolyte may have superior biocompatibility as compared toclassical electrolytes such as potassium hydroxide and zinc chloride.Contact lenses are stored in a “packing solution” which is typically amixture of sodium chloride, perhaps with other salts and bufferingagents such as sodium borate, boric acid, citric acid, citrates,bicarbonates, TRIS (2-amino-2-hydroxymethyl-1,3-propanediol),Bis-Tris(Bis-(2-hydroxyethyl)-imino-tris-(hydroxymethyl)-methane),bis-aminopolyols, triethanolamine, ACES(N-(2-hydroxyethyl)-2-aminoethanesulfonic acid), BES(N,N-Bis(2-hydroxyethyl)-2-aminoethanesulfonic acid), HEPES(4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid), MES(2-(N-morpholino)ethanesulfonic acid), MOPS(3[N-morpholino]-propanesulfonic acid), PIPES(piperazine-N,N′-bis(2-ethanesulfonic acid), TES(N-[Tris(hydroxymethyl)methyl]-2-aminoethanesulfonic acid), saltsthereof, phosphate buffers, e.g. Na2HPO4, NaH2PO4, and KH2PO4 ormixtures thereof. A formulation of packing solution has beendemonstrated as a battery electrolyte in combination with a zinc anodeand manganese dioxide cathode. Other electrolyte and electrodecombinations are possible.

A contact lens using a “salt water” battery may comprise an electrolytebased on sodium chloride, packing solution, or even a speciallyengineered electrolyte similar to tear fluid. In some examples, exposureto human tears could enable operation of the battery device.

In addition to, or instead of, possible benefits for biocompatibility byusing an electrolyte more similar to tears, or actually using tears, areserve cell may be used to meet the shelf life requirements of acontact lens product. Typical contact lenses are specified for storageof 3 years or more. This may be a challenging requirement for a batterywith a small and thin package. A reserve cell for use in a contact lensmay have a design similar to those shown in FIGS. 1 and 3, but theelectrolyte might not be added at the time of manufacture. As mentionedpreviously, the electrolyte may be stored in an ampule within thecontact lens and connected to the empty battery cell. One of thecavities of a laminar battery construct may also function to storeelectrolyte in a segregated fashion from the electrodes. In otherexamples, saline solution surrounding the contact lens, and thereforethe battery, may be used as the electrolyte. Within the contact lens andbattery package, a valve or port may be designed to keep electrolyteseparated from the electrodes until the user activates the lens. Uponactivation, perhaps by simply pinching the edge of the contact lens(similar to activating a glow stick), the electrolyte may be allowed toflow into the battery and form an ionic pathway between the electrodes.This may involve a one-time transfer of electrolyte or may expose thebattery for continued diffusion.

Some battery systems may use or consume electrolyte during the chemicalreaction. Accordingly, it may be necessary to engineer a certain volumeof electrolyte into the packaged system. This electrolyte may be storedin various locations including the separator or a reservoir.

In some examples, a design of a battery system may include a componentor components that may function to limit discharge capacity of thebattery system. For example, it may be desirable to design the materialsand amounts of materials of the anode, cathode, or electrolyte such thatone of them may be depleted first during the course of reactions in thebattery system. In such an example, the depletion of one of the anode,cathode, or electrolyte may reduce the potential for problematicdischarge and side reactions to not take place at lower dischargevoltages. These problematic reactions may produce, for example,excessive gas or byproducts which could be detrimental to safety andother factors.

Battery Architecture and Fabrication

Battery architecture and fabrication technology may be closelyintertwined. As has been discussed in earlier sections of the presentinvention, a battery has the following elements: cathode, anode,separator, electrolyte, cathode current collector, anode currentcollector, and packaging. Clever design may try to combine theseelements in easy to fabricate subassemblies. In other examples,optimized design may have dual-use components, such as, using a metalpackage to double as a current collector. From a relative volume andthickness standpoint, these elements may be nearly all the same volume,except for the cathode. In some examples, the electrochemical system mayrequire about two (2) to ten (10) times the volume of cathode as anodedue to significant differences in mechanical density, energy density,discharge efficiency, material purity, and the presence of binders,fillers, and conductive agents. In these examples, the relative scale ofthe various components may be approximated in the following thicknessesof the elements: Anode current collector=1 μm; Cathode currentcollector=1 μm; Electrolyte=interstitial liquid (effectively 0 μm);Separator=as thin or thick as desired where the planned maximalthickness may be approximately 15 μm; Anode=5 μm; and the Cathode=50 μm.For these examples of elements the packaging needed to providesufficient protection to maintain battery chemistry in use environmentsmay have a planned maximal thickness of approximately 50 μm.

In some examples, which may be fundamentally different from large,prismatic constructs such as cylindrical or rectangular forms, and whichmay be different than wafer-based solid state construct, a construct mayassume a pouch-like arrangement, using webs or sheets fabricated intovarious configurations with battery elements arranged inside. Thecontainment may have two films, or one film folded over onto the otherside, either configuration of which may form two roughly planar surfaceswhich may then be sealed on the perimeter to form a container. Thisthin-but-wide form factor may make battery elements themselves thin andwide. Furthermore, these examples may be suitable for applicationthrough coating, gravure printing, screen printing, sputtering, or othersimilar fabrication technology.

There may be numerous arrangements of the internal components, such asthe anode, separator and cathode, in these pouch-like battery exampleswith thin-but-wide form factors. Within the enclosed region formed bythe two films, these basic elements may be either co-planar, that isside-by-side on the same plane, or co-facial, which may be face-to-faceon opposite planes. In the co-planar arrangement, the anode, separator,and cathode may be deposited on the same surface. For the co-facialarrangement, the anode may be deposited on surface-1, the cathode may bedeposited on surface-2, and the separator may be placed between the two,either deposited on one of the sides, or inserted as its own separateelement.

Another type of example may be classified as laminate assembly, whichmay involve using films, either in a web or sheet form, to build up abattery layer by layer. Sheets may be bonded to each other usingadhesives, such as pressure-sensitive adhesives, thermally activatedadhesives, or chemical reaction-based adhesives. In some examples, thesheets may be bonded by welding techniques such as thermal welding,ultrasonic welding and the like. Sheets may lend themselves to standardindustry practices as roll-to-roll (R2R), or sheet-to-sheet assembly. Asindicted earlier, an interior volume for cathode may need to besubstantially larger than the other active elements in the battery. Muchof a battery construct may have to create the space of this cathodematerial, and support it from migration during flexing of the battery.Another portion of the battery construct that may consume significantportions of the thickness budget may be the separator material. In someexamples, a sheet form of separator may create an advantageous solutionfor laminate processing. In other examples, the separator may be formedby dispensing hydrogel material into a layer to act as the separator.

In these laminate battery assembly examples, the forming product mayhave an anode sheet, which may be a combination of a package layer andan anode current collector, as well as substrate for the anode layer.The forming product may also have an optional separator spacer sheet, acathode spacer sheet, and a cathode sheet. The cathode sheet may be acombination of a package layer and a cathode current collector layer.

Intimate contact between electrodes and current collectors is ofcritical importance for reducing impedance and increasing dischargecapacity. If portions of the electrode are not in contact with thecurrent collector, resistance may increase since conductivity is thenthrough the electrode (typically less conductive than the currentcollector) or a portion of the electrode may become totallydisconnected. In coin cell and cylindrical batteries, intimacy isrealized with mechanical force to crimp the can, pack paste into a can,or through similar means. Wave washers or similar springs are used incommercial cells to maintain force within the battery; however, thesemay add to the overall thickness of a miniature battery. In typicalpatch batteries, a separator may be saturated in electrolyte, placedacross the electrodes, and pressed down by the external packaging.

In a laminar cofacial battery, several methods to increase electrodeintimacy exist. The anode may be plated directly onto the currentcollector rather than using a paste. This process inherently results ina high level of intimacy and conductivity. The cathode, however, istypically a paste. Although binder material present in the cathode pastemay provide adhesion and cohesion, mechanical pressure may be needed toensure the cathode paste remains in contact with the cathode currentcollector. This may be especially important as the package is flexed andthe battery ages and discharges, for example, as moisture leaves thepackage through thin and small seals. Compression of the cathode may beachieved in the laminar, cofacial battery by introducing a compliantseparator and/or electrolyte between the anode and cathode. A gelelectrolyte or hydrogel separator, for example, may compress on assemblyand not simply run out of the battery as a liquid electrolyte might.Once the battery is sealed, the electrolyte and/or separator may thenpush back against the cathode. An embossing step may be performed afterassembly of the laminar stack, introducing compression into the stack.

Battery Element Sealing and Encapsulation

In some examples of battery elements for use in biomedical devices, thechemical action of the battery involves aqueous chemistry, where wateror moisture is an important constituent to control. Therefore it may beimportant to incorporate sealing mechanisms that retard or prevent themovement of moisture either out of or into the battery body. Moisturebarriers may be designed to keep the internal moisture level at adesigned level, within some tolerance. In some examples, a moisturebarrier may be divided into two sections or components; namely, thepackage and the seal.

The package may refer to the main material of the enclosure. In someexamples, the package may comprise a bulk material. The Water VaporTransmission Rate (WVTR) may be an indicator of performance, with ISO,ASTM standards controlling the test procedure, including theenvironmental conditions operant during the testing. Ideally, the WVTRfor a good battery package may be “zero.” Exemplary materials with anear-zero WVTR may be glass and metal foils. Plastics, on the otherhand, may be inherently porous to moisture, and may vary significantlyfor different types of plastic. Engineered materials, laminates, orco-extrudes may be hybrids of the common package materials.

The seal may be the interface between two of the package surfaces. Theconnecting of seal surfaces finishes the enclosure along with thepackage. In many examples, the nature of seal designs may make themdifficult to characterize for the seal's WVTR due to difficulty inperforming measurements using an ISO or ASTM standard, as the samplesize or surface area may not be compatible with those procedures. Insome examples, a practical manner to testing seal integrity may be afunctional test of the actual seal design, for some defined conditions.Seal performance may be a function of the seal material, the sealthickness, the seal length, the seal width, the sealing process, and theseal adhesion or intimacy to package substrates.

In some examples, the plurality of components comprising the laminarmicrobatteries of the present invention may be held together with apressure-sensitive adhesive (PSA) that also serves as a sealant. While amyriad of commercially available pressure-sensitive adhesiveformulations may exist, such formulations almost always includecomponents that may make them unsuitable for use within a biocompatiblelaminar microbattery. Examples of undesirable components inpressure-sensitive adhesives may include low molecular mass leachablecomponents, antioxidants e.g. BHT and/or MEHQ, plasticizing oils,impurities, oxidatively unstable moieties containing, for example,unsaturated chemical bonds, residual solvents and/or monomers,polymerization initiator fragments, polar tackifiers, and the like.

Suitable PSAs may on the other hand exhibit the following properties.They may be able to be applied to laminar components to achieve thinlayers on the order of 2 to 20 microns. As well, they may comprise aminimum of, for example, zero undesirable or non-biocompatiblecomponents. Additionally, they may have sufficient adhesive and cohesiveproperties so as to bind the components of the laminar battery together.And, they may be able to flow into the micron-scale features inherent indevices of the present construction while providing for a robust sealingof electrolyte within the battery. In some examples of suitable PSAs,the PSAs may have a low permeability to water vapor in order to maintaina desirable aqueous electrolyte composition within the battery even whenthe battery may be subjected to extremes in humidity for extendedperiods of time. The PSAs may have good chemical resistance tocomponents of electrolytes such as acids, surfactants, and salts. Theymay be inert to the effects of water immersion. Suitable PSAs may have alow permeability to oxygen to minimize the rate of direct oxidation,which may be a form of self-discharge, of zinc anodes. And, they mayfacilitate a finite permeability to hydrogen gas, which may be slowlyevolved from zinc anodes in aqueous electrolytes. This property offinite permeability to hydrogen gas may avoid a build-up of internalpressure.

FIGS. 13A-13C illustrate exemplary designs for sealing and encapsulatinga biocompatible energization element. Elements of FIGS. 13A-13C may beconsistent with the elements of previous illustrations. Beginning withFIG. 13A, a top-down view of an exemplary biocompatible energizationelement with encapsulation is illustrated. An envelope capable ofsealing 1301 may encapsulate the energization element containing atleast an anode current collector 1302 with anode, a cathode currentcollector 1304 with cathode, and internal adhesives/sealants 1308. Theenvelope capable of sealing 1301 may comprise polymer films capable ofsealing such as polypropylene. The internal adhesives/sealants 1308 maycomprise pressure sensitive adhesives such as polyisobutylene.

Polyisobutylene (PIB) is a commercially-available material that may beformulated into PSA compositions meeting many if not all desirablerequirements. Furthermore, PIB may be an excellent barrier sealant withvery low water absorbance and low oxygen permeability. An example of PIBuseful in the examples of the present invention may be Oppanol® B15 byBASF Corporation. Oppanol® B15 may be dissolved in hydrocarbon solventssuch as toluene, heptane, dodecane, mineral spirits, and the like. Oneexemplary PSA composition may include 30 percent Oppanol® B15 (w/w) in asolvent mixture, including 70 percent (w/w) toluene and 30 percentdodecane. The adhesive and rheological properties of PIB-based PSA's maybe determined in some examples by the blending of different molecularmass grades of PIB. A common approach may be to use a majority of lowmolar mass PIB, e.g. Oppanol® B10 to effect wetting, tack, and adhesion,and to use a minority of high molar mass PIB to effect toughness andresistance to flow. Consequently, blends of any number of PIB molar massgrades may be envisioned and may be practiced within the scope of thepresent invention. Furthermore, tackifiers may be added to the PSAformulation so long as the aforementioned requirements may be met. Bytheir very nature, tackifiers impart polar properties to PSAformulations, so they may need to be used with caution so as to notadversely affect the barrier properties of the PSA. Furthermore,tackifiers may in some cases be oxidatively unstable and may include anantioxidant, which could leach out of the PSA. For these reasons,exemplary tackifiers for use in PSA's for biocompatible laminarmicrobatteries may include fully or mostly hydrogenated hydrocarbonresin tackifiers such as the Regalrez series of tackifiers from EastmanChemical Corporation.

Next, FIG. 13B illustrates an exemplary bottom-up view of abiocompatible energization element with encapsulation. FIG. 13Billustrates the capability of the plastic envelope capable of sealing1301, to be sealed at different exemplary sealing sites 1306. In someexamples, seals may be formed by a welding process that may involvethermal, laser, solvent, friction, ultrasonic, or arc processing. Inother examples, seals may be formed through the use of adhesive sealantssuch as glues, epoxies, acrylics, natural rubber, and synthetic rubber.Other examples may derive from the utilization of gasket type materialthat may be formed from cork, natural and synthetic rubber,polytetrafluoroethylene (PTFE), polypropylene, and silicones to mentiona few non-limiting examples.

FIG. 13C illustrates an exemplary long-edge view of a biocompatibleenergization element with encapsulation containing an anode currentcollector 1302 with anode, a cathode current collector 1304 with cathodeblend 1312, a separator 1310 placed on a separator shelf 1311,adhesive/sealant 1308, and multiple exemplary sealing sites 1306. Aftertreating the envelope capable of sealing 1301 with, for example heattreatment, the envelope may enclose the components of the biocompatibleenergization element from the top and the bottom; however, the endscontaining the anode current collector 1302 and cathode currentcollector 1304 may still be susceptible to leak. Thus, the addition ofsealing sites 1306 may become necessary. The current collector sealingsites may be sealed by several sealing methods including, for example,the use welding, adhesives, lacquer, epoxy, asphalt, or heat treatingthe PSAs.

In some examples, the energization elements according to the presentinvention may be designed to have a specified operating life. Theoperating life may be estimated by determining a practical amount ofmoisture permeability that may be obtained using a particular batterysystem and then estimating when such a moisture leakage may result in anend of life condition for the battery. For example, if a battery isstored in a wet environment, then the partial pressure differencebetween inside and outside the battery may be minimal, resulting in areduced moisture loss rate, and therefore the battery life may beextended. The same exemplary battery stored in a particularly dry andhot environment may have a significantly reduced expectable lifetime dueto the strong driving function for moisture loss.

Methods of Sealing and Encapsulation for Biocompatible EnergizationElements

FIGS. 14A-14I illustrate exemplary method steps for sealing andencapsulating a biocompatible energization element. The method steps ofFIG. 14A-14I may be performed by stacking layers of material upon oneanother, building a laminar structure, as described and illustratedherein. Beginning with FIG. 14A, a first polymer film capable of sealing1401, such as polypropylene may be obtained. Next, at FIG. 14B, acathode current collector 1404 may be placed on top of the polymer filmcapable of sealing 1401. The cathode current collector 1404 may be linedon an outer edge by adhesive/sealant 1408 which may be useful foradhering the layers together. At FIG. 14C, a cathode blend 1412 may bedeposited upon the cathode current collector 1404. The cathode blend1412 may be formulated in such a manner to include adhesive and cohesiveproperties in order to adhere to itself and to its neighboring layers.At 14D, a separator shelf 1411 may be placed on the cathode currentcollector 1404 where it may make contact with sealant/adhesive 1408 inorder to adhere to the existing structure. The separator shelf 1411 maybe added to the laminate structure in such a way as to leave a voidacross the length of the laminate structure where the cathode blend 1412rests. This void may be useful in creating a cavity wherein the cathodeblend 1412 may rest. Next, at FIG. 14E, a separator 1410 may be placedupon the separator shelf 1411 and the cathode blend 1404.

At FIG. 14F, an anode 1402, which may include an anode currentcollector, may be added to the laminar structure to rest upon theseparator 1410. Adhesive/sealant 1408 may be added to the anode currentcollector 1402, similar to the cathode current collector 1404, in orderto adhere the layers together. Next, at FIG. 14G, a second polymer filmcapable of sealing 1401, such as polypropylene may be obtained andplaced upon the anode current collector 1402, adhered byadhesive/sealant 1408, thus encapsulating the top and bottoms layers ofthe laminar structure.

FIG. 14H illustrates an exemplary laminar structure after treating theends of the laminar structure at the adhesive/sealant 1408 sites with afinal sealing means such as laser welding, ultrasonic welding, or othersimilar means of welding. Once sealing at the adhesive/sealant isaccomplished, current collector interconnects, such as an anodeinterconnect 1412 and a cathode interconnect 1414, should be freelyavailable outside of the encapsulated laminar structure. FIG. 14Iillustrates an exemplary embodiment of a final encapsulation stepwherein all sides of the laminar structure have been sealed leaving onlycurrent collector interconnects exposed. Sealing of the laminarstructure may be accomplished by different combination of sealing andadhering means. For example, assuming the laminar structure is arectangular in shape wherein the rectangle consists of two long edgesand two short edges, the long edges may be laser welded while the shortedges may be adhered by PSAs, or vice versa. Alternatively, the edges ofthe laminar structure may be uniformly sealed entirely by welding, orentirely by PSAs. The type of seal may depend on the characteristics ofthe seal, and the need for complete sealing compared to the need forsome level of permeability.

FIGS. 15A-15D illustrate exemplary cross-sectional views of theexemplary energization element illustrated in, for example, FIG. 14G.In. FIG. 15A, an exemplary energization element is illustrated withenergization components comprising a top and bottom polymer film capableof sealing 1501, an anode current collector 1502 with anode, a cathodecurrent collector 1504 with cathode blend 1512, a separator 1510 placedupon a separator shelf 1511, and adhesive/sealant 1508. The viewdepicted in FIG. 15A may be considered a “long-edge” view of theenergization element, whereas the view depicted in FIGS. 15B-15D may beconsidered a “short-edge” view of the energization element.

Next, at FIG. 15B, a short-edge view of an energization elementillustrates exemplary components placed upon one another. The polymerfilm capable of sealing 1501, adhesive/sealant 1508, and separator shelf1511 may all comprise similar materials thus enabling their ability tomeld together. After treating the energization element with, for exampleheat or laser treatment, the polymer film capable of sealing 1501 maybegin to seal and envelop the components of the biocompatibleenergization element while also melding with the adhesive/sealant 1508,the separator shelf 1511, or both, as exemplified in FIG. 15C. Themelding of the components may occur on at least one edge of theenergization element encapsulation. Finally, at FIG. 15D, an exemplaryfinal view of a short-edge of an energization element is illustratedwhere the polymer film capable of sealing 1501 has enveloped severalcomponents of the energization element by melding with a separator shelf1511. In some examples, the polymer film capable of sealing 1501 maymeld directly to a separator as opposed to a separator shelf 1511. Theseparator shelf may further encapsulate and seal the energizationelement by adhering to adhesive/sealant 1508, which in turn may adhereto an interconnect such as a cathode current collector 1504.Alternatively, the polymer film capable of sealing 1501 may be treatedin such a manner (heat, ultrasonic, and the like) to meld with thepolymer film capable of sealing 1501 given the similarity in material.Further, the polymer film capable of sealing 1501 may be metalized insuch a way to then be able to meld directly to a metal interconnect,such as a cathode current collector 1504.

One alternative to the placement of electrodes as depicted in FIGS.15A-15D may be to insert the electrodes into the laminar structure afterpartial sealing of the polymer layers capable of sealing. This may beaccomplished through such methods as injecting the electrodes into theirrespective positions.

One alternative to the exemplary method steps illustrated in FIGS.14A-14I may be the exemplary method steps illustrated in FIGS. 16A-16G.FIGS. 16A-16G illustrate exemplary method steps for sealing andencapsulating a biocompatible energization element wherein, instead ofbuilding in a step wise bottom-to-top approach, two distinct halves maybe built separately, then converge to complete a laminar structure.FIGS. 16A-16C illustrate exemplary method steps for building a bottomsegment of the laminar structure while FIGS. 16D-16G illustrate a topsegment. Beginning with FIG. 16A, a cathode current collector 1604 maybe placed on top of a polymer film capable of sealing 1601. The cathodecurrent collector 1604 may be lined on an outer edge by anadhesive/sealant 1608 which may be useful for adhering the layerstogether. Next, at FIG. 16B, a separator shelf 1611 may be placed uponthe anode current collector 1604, where it may make contact withadhesive/sealant 1608 in order to adhere to the existing structure. Theseparator shelf 1611 may be added to the laminar structure in such a wayas to leave a void across the length of the laminate structure. This maybe accomplished by, for example, inserting two distinct separatorshelves, one on each side of the anode current collector 1604, or byplacing a solid sheet of separator shelf across the anode currentcollector 1604, then processing out a middle segment of the separatorshelf by, for example, cutting out a middle piece of separator shelf.This void that is created by adding the separator shelf 1611 may beuseful in creating a cavity wherein a cathode blend may eventually rest.At FIG. 16 C, a cathode blend 1612 may be applied to the laminarstructure, into the cavity. The cathode blend 1612 may be applied to thelaminar structure by several means, for example, squeegee application,printer application, needle application, or other means of applying aviscous blend into a cavity.

FIGS. 16D-16G illustrate the exemplary method steps for building a topsegment of a laminar structure. At FIG. 16D, an anode and anode currentcollector 1602 may be placed upon of a polymer film capable of sealing1601. The anode and anode current collector 1602 may be lined on anouter edge by adhesive/sealant 1608 which may be useful for adhering thelayers together. Next, at FIG. 16E, a separator 1610 may be placed uponthe anode and anode current collector 1602. At FIG. 16F, the structuresdepicted in FIG. 16C and FIG. 16E may be combined, one on top of theother, in such a manner as to lineup the adhesive/sealant 1608 of thestructures. Once combined, the cathode blend 1612 may disperse into thecavity while still maintaining contact with the separator 1610, theseparator shelf 1611, and the cathode current collector 1604. FIG. 16Gillustrates an exemplary laminar structure after treating the ends ofthe laminar structure at the adhesive/sealant 1608 sites with a finalsealing means such as laser welding, ultrasonic welding, or othersimilar means. Once sealing at the adhesive/sealant is accomplished,current collector interconnects, such as an anode interconnect 1612 anda cathode interconnect 1614, should be freely available outside of theencapsulated laminar structure.

Biocompatible energization elements typically require an electrolyte.The electrolyte may be pre-wet onto the cathode and separator prior toassembly. The electrolyte may be dispensed onto the cathode and/orseparator after they have been placed into the package. Electrolyte maybe added just prior to placement of the top package, or alternatively,may be dispensed into the cell through a needle after partial sealing ofthe cell.

Sealing of the laminar structure may be accomplished by differentcombination of sealing and adhering means. For example, assuming thelaminar structure is rectangular in shape, wherein the rectangleconsists of two long edges and two short edges, the long edges may belaser welded while the short edges may be adhered by PSAs, or viceversa. Alternatively, the edges of the laminar structure may beuniformly sealed entirely by welding, or entirely by PSAs. The type ofseal may depend on the characteristics of the seal, and the need forcomplete sealing compared to the need for some level of permeability.The sealing may occur as a result of: sealing the top polymer filmcapable of sealing to the bottom polymer film capable of sealing;sealing the polymer film directly to the separator shelf; sealing ametalized version of the polymer film to the current collector; or anyother similar methods of sealing the laminar structure.

Additional Package and Substrate Considerations in Biocompatible BatteryModules

There may be numerous packaging and substrate considerations that maydictate desirable characteristics for package designs used inbiocompatible laminar microbatteries. For example, the packaging maydesirably be predominantly foil and/or film based where these packaginglayers may be as thin as possible, for example, 10 to 50 microns.Additionally, the packaging may provide a sufficient diffusion barrierto moisture gain or loss during the shelf life. In many desirableexamples, the packaging may provide a sufficient diffusion barrier tooxygen ingress to limit degradation of zinc anodes by direct oxidation.

In some examples, the packaging may provide a finite permeation pathwayto hydrogen gas that may evolve due to direct reduction of water byzinc. And, the packaging may desirably sufficiently contain and mayisolate the contents of the battery such that potential exposure to auser may be minimized.

In the present invention, packaging constructs may include the followingtypes of functional components: top and bottom packaging layers, PSAlayers, spacer layers, interconnect zones, filling ports, and secondarypackaging.

In some examples, top and bottom packaging layers may comprise metallicfoils or polymer films. Top and bottom packaging layers may comprisemulti-layer film constructs containing a plurality of polymer and/orbarrier layers. Such film constructs may be referred to as coextrudedbarrier laminate films. An example of a commercial coextruded barrierlaminate film of particular utility in the present invention may be 3M®Scotchpak 1109 backing which consists of a polyethylene terephthalate(PET) carrier web, a vapor-deposited aluminum barrier layer, and apolyethylene layer including a total average film thickness of 33microns. Numerous other similar multilayer barrier films may beavailable and may be used in alternate examples of the presentinvention.

In design constructions including a PSA, packaging layer surfaceroughness may be of particular importance because the PSA may also needto seal opposing packaging layer faces. Surface roughness may resultfrom manufacturing processes used in foil and film production, forexample, processes employing rolling, extruding, embossing and/orcalendaring, among others. If the surface is too rough, PSA may be notable to be applied in a uniform thickness when the desired PSA thicknessmay be on the order of the surface roughness Ra (the arithmetic averageof the roughness profile). Furthermore, PSA's may not adequately sealagainst an opposing face if the opposing face has roughness that may beon the order of the PSA layer thickness. In the present invention,packaging materials having a surface roughness (Ra) less than 10 micronsmay be acceptable examples. In some examples, surface roughness valuesmay be 5 microns or less. And, in still further examples, the surfaceroughness may be 1 micron or less. Surface roughness values may bemeasured by a variety of methods including but not limited tomeasurement techniques such as white light interferometry, stylusprofilometry, and the like. There may be many examples in the art ofsurface metrology that surface roughness may be described by a number ofalternative parameters and that the average surface roughness, Ra,values discussed herein may be meant to be representative of the typesof features inherent in the aforementioned manufacturing processes.

Specific examples have been described to illustrate sample embodimentsfor the methods of sealing and encapsulation for biocompatiblebatteries. These examples are for said illustration and are not intendedto limit the scope of the claims in any manner. Accordingly, thedescription is intended to embrace all examples that may be apparent tothose skilled in the art.

What is claimed is:
 1. A biomedical device comprising: a. anelectroactive element, wherein the electroactive element undergoes aphysical or chemical change in response to an electrical signal; b. acircuit; c. a biocompatible energization element, wherein thebiocompatible energizing element comprises: a first and second currentcollector, i. a cathode, ii. an anode, iii. an electrolyte, iv. alaminar stack structure comprising a first and a second laminarconstruct release layers; and first and second laminar constructadhesive layers located between the first and second laminar constructrelease layers; and a laminar construct core located between the firstand second laminar construct adhesive layers, and v. a firstencapsulation for the energization element, wherein the firstencapsulation is a polymer film capable of sealing, wherein the polymerfilm capable of sealing is treated to form a seal with itself and withelements of the biocompatible energization element; and d. a secondencapsulation that encapsulates the electroactive element, the circuit,and the biocompatible energization element.
 2. The biomedical device ofclaim 1 wherein the laminar stack structure comprises a cavitystructure.
 3. The biomedical device of claim 1 wherein the polymer filmcapable of sealing comprises polypropylene.
 4. The biomedical device ofclaim 1 wherein the polymer film capable of sealing is treated by ameans of welding.
 5. The biomedical device of claim 4 wherein thepolymer film capable of sealing is further adhered to the biocompatibleenergization element with adhesive.
 6. The biomedical device of claim 4wherein the polymer film capable of sealing is welded to a separatorcontained within the biocompatible energization element.
 7. Thebiomedical device of claim 4 wherein the polymer film capable of sealingis welded to a separator shelf contained within the biocompatibleenergization element.
 8. The biomedical device of claim 4 wherein thepolymer film capable of sealing is welded to a current collector of thebiocompatible energization element.
 9. The biomedical device of claim 8wherein the biomedical device is an ophthalmic device.
 10. Thebiomedical device of claim 9 wherein the ophthalmic device is a contactlens.
 11. The biomedical device of claim 8 wherein biomedical device isa surgical device.
 12. The biomedical device of claim 1 wherein thecircuit comprises an integrated circuit.
 13. The biomedical device ofclaim 1 wherein the second encapsulation comprises a hydrogel.
 14. Abiomedical device comprising: a. a circuit; b. a biocompatibleenergization element, wherein the biocompatible energizing elementcomprises: a first and second current collector, i. a cathode, ii. ananode, iii. an electrolyte, iv. a laminar stack structure comprising atleast a portion of the cathode, the anode, the electrolyte, and aseparator formed at least in part from a UV-curable hydrogel formulationwherein the separator forms a barrier between the cathode and the anode,and v. a first encapsulation for the energization element, wherein thefirst encapsulation is a polymer film capable of sealing, wherein thepolymer film capable of sealing is treated to form a seal with itselfand with elements of the biocompatible energization element; and c. asecond encapsulation that encapsulates the electroactive element, thecircuit, and the biocompatible energization element.
 15. The biomedicaldevice of claim 14 wherein the laminar stack structure comprises acavity structure.
 16. The biomedical device of claim 14 wherein thepolymer film capable of sealing comprises polypropylene.
 17. Thebiomedical device of claim 14 wherein the polymer film capable ofsealing is treated by a means of welding.
 18. The biomedical device ofclaim 17 wherein the polymer film capable of sealing is further adheredto the biocompatible energization element with adhesive.
 19. Thebiomedical device of claim 17 wherein the polymer film capable ofsealing is welded to a separator contained within the biocompatibleenergization element.
 20. The biomedical device of claim 17 wherein thepolymer film capable of sealing is welded to a separator shelf containedwithin the biocompatible energization element.